PIED or my fault?

My SO has been having issues with ED for nearly two years it became really bad at one point when I discovered the extent of his porn use and was upset as our sex life was suffering. At the time he put the loss of libido and ED down to things being strained between us but after about 6 months he mentioned that he was also having issues staying hard when he was M (with and without P) and that he was not getting morning erections - this prompted him to get some pills. They work fine, he only needs to take 1/4 now for them to be effective. At that point he admitted that the ED was 'possibly' related to porn use but my attitude with him didn't help (I would get upset after discovering each time, would niggle him about looking a insta all the time etc).

Things have been fine for a while, the ED can still be an issue at times - we have sex occasionally without the pills and he does lose some stiffness but is normally ok to carry on - the only time it really fails is when he is on his knees. On the occasions when he has used again (he doesn't have a PA so once in a while shouldn't be an issue - his words not mine) and I find out, I get upset and we usually have an argument - this is when it always fails and can take a few weeks to get back to 'usable' condition (sorry for the terminology). I would agree that he was never a massively excessive user (based on what I have read on here) - periods of PMO every day followed by times when it would only be once or twice a week but he is 53 and has been using internet porn since for probably the last 20 yrs (or since it became easily accessible). Just to add context the ED became problematic when he was using daily.

I am more than happy to take some responsibility for these occasions as I am well aware that anxiety can be a massive issue but he is now adamant that he has never had PIED as he was never that big a user and that this is more to do with me than him.

Your thoughts (even if you think its not what I want to hear) would help?