I think ejaculation is the real problem, not porn or masturbation. Ejaculating while having sex might negate some of the negative effects, it's still a stressor for the male body though.
The real danger of porn is that you will make masturbation and ejaculation a (often daily) habit. You will ejaculate on days when your libido is so low that you would not even be able to get an erection without the help of porn. Which is a pretty good sign that your body is in no place whatsoever to just waste your man juice for the heck of it.
That being said, I feel best ejaculating 1-2 times per month.
A lot less food allergies, pretty much no more acne and more confidence compared to my old every day habit.
I feel like completely abstaining from ejaculation does not provide any extra benefits for me and I will start to get random boners in public and wet dreams at some point. 1-2 times per month is the minimum that prevents that from happening for me.
I'm not in a relationship at the moment, so sex is a relatively rare thing for me right now.
Having sex pretty much everyday but only ejaculating 1-2 times per month seems doable though and would be considered ideal by taoist/tantra philosophies.
Edit: When I started doing the no ejaculation thing my libido was pretty much nonexistent for the first 2-3 months. At some point it came back with a vengeance and I started feeling like a horny 14 year old teenager again.
I also feel like oysters and liver are almost a must if you try to recover from over-ejaculation induced damage, especially if you have skin problems (at least they were for me)
There's a reason why oysters are considered an aphrodisiac.