If you have painful erections, because of phimosis, go to the doctor. You probably need a circumcision or part of your foreskin removed. I don’t think it’s healthy to ejaculate while suppressing an erection.
Do NOT listen to the person who said give up masturbation all together, it's healthy and normal. You do seem to be having issues though, so a break to rewire your brain might be good.
I've read about this. So, yes. You've trained your body/brain to ejaculate when flaccid and you have to untrain it. Are you uncircumcised? That's usually the case when a dude does this. You need to give up masturbating completely for a while. And when you go back, don't give in and masturbate in that same way. The issue is that when you are with a woman this won't work. And I assume you'd like a regular sex life at some point. So, cold turkey to readjust and don't continue this when you resume down the road.
Yes it is. Your artificially have sex...by yourself or watching other people have sex. Drop porn and masturbation alltogether. This will strengthen back your testosterone over time and bring you back to normal seeking a better life and real women.