Secret cell phone to watch porn? Or am I crazy?

I've been in my relationship for a few months short of two years. At the beginning of our relationship, my boyfriend had a hard time cumming when we would have sex. It barely happened. It crushed my self esteem. We wanted to figure it out to improve our relationship, and upon research discovered pmo induced ed. I knew he was watching porn regularly and really wasn't concerned about it. He said that he would try to cut down on his pmo and admitted he probably did it too often. So he tried... sex improved slightly, but he still was experiencing loss of erection with me. My self esteem was completely crushed now. Once I realized the porn was why he would lose an erection with me, and to keep his erection and orgasm with me he had to close his eyes, I felt so extremely unattractive and unimportant to him. I told him I didn't want porn in our relationship at all anymore. He agreed he would cut out the porn to save our relationship. He tried and failed between 5-10 times over the span of several months. Each time he failed he would act like I was crazy for accusing him and he would lie extremely convincingly. But I would know and he would eventually tell the truth, sometimes after keeping the lie up for several days and making me feel like I was crazy for accusing him. I stressed the importance of honesty and truth and please just tell me.the truth so we can move.past this, but he always would lie.
Fast forward to about a year into our relationship... I am full of anxiety every day at work thinking he is home pmoing . It is driving me insane. As far as I know he is cut back to about once a month or so, but has never been upfront with me unless caught so how do I know for sure. I ask him to install ever accountable on his phone and computer so I can have some peace of mind. He agrees.
Things got much better but I was left with betrayal trauma and not a lick of trust in this man that I love. I know when it comes down to it he will choose thousands of naked porn stars over me, and he will lie to my face repeatedly that he did not. So despite the ever accountable, I am still paranoid and untrusting.
I worry he is going to his mother's house and using her computer. I woŕrried he was using his work computer. I worried he was using an alternate hard drive that did not have ever accountable on it. I live daily in fear of being lied to again.
After some time I am somewhat satisfied all is well. But about once a month a wave of anxiety hits me and I am unable to stop worrying about it so I bring it up with him. He gets angry that I still can't trust him after all of this time. It has been about 8 months since ever accountable was installed and since my last proof of his viewing porn.
Things were going ok, then I checked the history on our router of what devices have been signing into our internet.
I find that an iPhone signed in on March 2nd, an hour after I went to sleep. It only stayed connected to our Wi-Fi for 15 minutes.
Earlier that day he had gone to a pawn shop without me to look at second hand electronics. Returned and said he didn't buy anything.
On March 11th, this unknown iPhone signed on again, and again about 1 hour after I went to sleep. This session also lasted only 15 minutes.
March 22nd, he was late coming home from work. He went to his mother's to check her thermostats and mail as she is away. He spent 45 minutes at his mother's empty house. He claims he had to go to the bathroom and this is why it took him so long. I questioned him on it, asking if he used his mom's computer. I ask him to please tell me of any secret he has, please be honest so we can work through things. He tells me I am crazy and he should be able to go to the bathroom without me accusing him of pmo. I am really looking for him to tell me about the iPhone. He gives me no information and just makes me feel crazy.
I check the Wi-Fi history and notice that the unknown iPhone connected at the exact same time as his phone connected when he got home from his mother's that day, which would be when he walked into the house. I remember when he came in he went to the bedroom first. The iPhone that connected when he walked in was disconnected 3 minutes later.
If a Wi-Fi connection is saved in a phone, and the phone is on, it connects automatically. My assumption is that the phone was on from using it at his mother's house for those 45 minutes, he comes home, realizes it is on, turns it off. Hence the 3 minute connection.
That night, I fall asleep on the couch. About an hour after I fall asleep, the iPhone connects to Wi-Fi. This time it stays connected for 40 minutes instead of the usual 15.
Unfortunately this behavior lines up. A few days prior I had set up open dns on our router to attempt to stop the iPhone from connecting to porn. I know VPN apps can be used as a work around, but I wanted to attempt to stop it.
The first-time the phone is used on our Wi-Fi after the dns is installed, the user spends 45 minutes on it. Assuming this is because they had to figure out how to get around it and install an app that would allow them to view porn.
It all so sadly makes sense that it is my boyfriend.
We have a password on our Wi-Fi, whoever is connecting guessed the password correctly on the first try as the logs on the router tell me. We do not hang out with anyone in our apartment building and they do not know our password. It is very very slight chance that someone could guess it, but on the first try?
Also... who breaks into and steals a neighbors Wi-Fi to use it only for 15 minutes once every 10 days. If someone was stealing our Wi-Fi they wouldn't have their own and would be connected much more often.
It breaks my heart that the circumstances all add up to the fact that my boyfriend has a secret phone to view porn on with or being caught by ever accountable.
A few weeks prior to today we were talking about it all and he mentioned that we never really knew for sure that it was porn that was making him suffer ed. He tried to say we were drinking a lot then and he was nervous about ed which could have been the cause. He was trying to downplay porns role in all of this. I wondered if he then went and bought a phone to do this on so he can know if he can still watch porn and also have sex with me. Even without the ed, I am no longer willing to be in a relationship with a man that watches porn. It broke my heart and made me feel worthless, and I view it as betrayal and cheating now. I have been chosen second to porn too many times nd I will not be put in that position again.
So all of this happens, and thus weekend I just can't stand not asking him about the phone. I expect him to tell me the truth in the face of my evidence.
Instead he tells me I am nuts. He cannot go on any longer with me not trusting him. He has done no wrong, has no secret cell phone, has not looked at porn since I last caught him. He gets very very angry. He says he has no idea what this phone is or why it lines up with the timeline. He is as baffled as I am but swears it is not him. He even says that for a moment he thought I was making it all up so that I would have a reason to break up with him.
He makes me feel so awful and untrusting and like I am ruining what is am otherwise wonderful relationship by refusing to get over his past lies and trust him.
He says if he was going to do that he certainly wouldn't buy an iphone(he hates iphones), and that he just wouldn't do that. That he has no desire to watch porn anymore. He is so very convincing and when I am talking to him about it, I mostly believe he is telling the truth.
But then reality comes crashing down and I realize that the Wi-Fi connection info is so many circumstances that cannot be explained. How did someone get our password the first time. Why do they sign on 15 minutes at a time only once every 10 or so days. Why are they only ever signed on when I am fast asleep. Why did they spend over twice as long online the day after I installed open dns.
I really do feel like I am going crazy and this is consuming my being. I have two beautiful children and my mind cannot be there with them as this is always at the back of my mind.
I need the truth.
If I could get into his mom's router I could see if the iPhone connected there when he was checking her house.
But I don't have the router password, only the Wi-Fi.
He said to leave the password the same so that we can see if the iPhone connects when we are together sometime, that can prove it is not him. It hasn't connected though since I told him about it. I am having trouble sleeping as I want to be awake when it connects to see that he is sleeping too.
He said that if I don't begin to trust him and if I can't forget about this he will have to break up with me as my suspicion is making him miserable. So I cannot even keep talking to him about it. I just don't know what to do.
Please help!!