I only discovered the existence of POIS a few days ago but from the short time I've had to research it, it's clear it gets triggered differently for different people and the effects are vastly different also, so I can only talk from my personal experience here, which in this case appears opposite to yours.
I've watched porn, very frequently, for over 20 years yet my (suspected) POIS issues only started 3 years ago, fairly short into a new relationship, which is still ongoing to this day. I suspect my POIS is not triggered when masturbating, which in 90% of the time involves porn, or if it does trigger it, its consequences are definitely not as severe compared to those I endure from actual sex. I can't say much about feeling guilty about watching porn, that's a very personal thing, depending on a lot factors but personally I've never felt guilty about watching porn so it's a non issue for me.
Also, I've masturbated for over 15 years without lube or anything and never had any issues. I just wasn't aware of its existence at the time. Well, that's not true, I did see American Pie where the main character brings out the lube in a certain scene but using lube was something very American at the time for me ... until much later when I discovered not having used it had had serious consequences on sensitivity but that's a whole other story, which I wrote about in my initial post).
Anyway, as @Danmh already asked, is there a consistent and repeatable difference between when you use porn and when you don't? It's one of the easier things to test so I would certainly recommend doing that.
