On the sex, porn use side, sounds like he needs to get out of the habit he's gotten into of using it - so that he has the drive and motivation to have sex with his partner more.
Porn (putting aside the huge ethical debate) is quick, easy, convenient, selfish, and ultimately pretty lazy. He sounds like he needs to stop or at least minimise its use and get back in track with a realised life; as the priority.
(Related to that is the separate point that you sound like you were unhappy about him using porn to masturbate and that he said he now found if extremely difficult to do so without it.
Well that can be undone/broken - but would take him making the effort to not use porn, use his imagination and perservere until he's getting there without porn. Again, bit the lazy, quick, east option but it might help your overall sex life too).
On the subject of your relationship, I do agree that it's unhealthy. Actually I don't know how someone decent could let you work in your job, look after your disabled mum, do absolutely everything with/for your kids and on top of all that .. let you wait in him hand and foot. That doesn't say very good things about his character. At best it says he's thoughtless, entitled and a bit selfish.
However it's you who's been doing it (as well as him letting you do it) - I have no idea where you got this martyred, stepford wife, slave mentality from but it's unhealthy. I dint know how you haven't cracked before now, even when your three kids were young (bit sure how old they are now) .. I don't understand how you haven't had a mental breakdown.
You mentioned you being enough for him; that seemed to be about porn/sex but in general I get this impression of you feeling like you have to fulfil some idealised, (extremely traditional) perfect image of housekeeper, mum, wife, lover etc. etc.
He's not perfect, (see above, he should never have let you become like a domestic servant but especially not after having kids and especially not after you needed to become a carer for your mum), never has been. Why do you have to be?
Lots of "flawed" people are loved and gave good partners.
It's going to be an interesting process to try to change the status quo you've established since young and naive in your relationship and household (!)
On the sex thing - your DH realising you are angry and hurt and taking it seriously might be a good thing now, but ultimately it would be best to talk about this and say you feel you no longer have a healthy, fulfilling sex life because he's fulfilling (too much of) his sexual needs with porn. And that he needs to reduce his porn use (or just stop). And try to see what he thinks is causing the situation, if there is anything else. You shouldn't have to raise this with him if he wasn't being selfish, lazy and inconsiderate but there it is.