Serious questions about my journey so far and need guidance badly. Relapsed on Day 20

Intro: I am 29M. I have been PMO since 17. Mostly vanilla but got into extreme/hardcore around 1.5 yr back. I had issues getting the little one up when it came to real encounters recently and have taken the nofap and brain-rewiring journey much seriously since then.

Progress since starting NoFap: Started noticing strong MW as I entered the second week. MW stays for a few min after I wake up but not longer than that. Not sure how far I have come in the journey. I experienced flatline for the first week and I was super nervous the whole time. I am also able to get it up by imagining various scenarios but I definitely feel it has been difficult as compared to a year ago.

I will go straight to some of the fundamental questions I have about the whole process

Questions:

1. Is it really a relapse if I haven't masturbated to porn?
   
   
2. I noticed that I am thinking way too much about getting my penis up whenever I watch a hot scene or woman. I am also getting concerned if I am not able to get my penis up on-demand thinking I am not making any progress in my journey. Can someone please advise me how to deal with this?
   
   
3. I noticed that I am able to get my penis up when I recollect some of my previous encounters or imagine new scenarios. But I am not able to keep it hard for more than a couple of min. Should I be concerned about this?
   
   
4. Lastly, how to objectively measure progress in this aspect?
   

Thank you very much for all the help. This sub is a life-saver.