Struggling to make a final decision

I'm really struggling here. My spouse (40m) and I (36f) have been together 17 years, married 12. He has taken to being on the computer and playing games and napping the majority of it, even with 3 kids. I do 95% of literally everything, from household chores and maintenance, caring for the children, to buying him his clothing and shoes. Our sex life is non existent. He's a very numb person with very little emotion. I've asked him to give therapy a chance, which he's agreed, but in all these years has never once made the call. He doesn't help with anything unless I ask over and over again. I'm tired of having a 4th child and not a partner who wants to enjoy life with me. I've been in therapy for awhile and have decided I want a divorce. I'm 99.9% sure of this. I've expressed my feelings and needs over the years and am always met with little change and then right back into his own routine of gaming and napping. I stated having a conversation with him 6 months ago about considering a divorce. At that point, I was still wanting to save our marriage. I asked him to go to therapy with me, but he shrugged it off. I finally got him to go to one session, and was met with "this won't fix us", which I agreed - we have to do the work ourselves. Our 2nd appointment he didn't want to go, so I canceled and just continued going solo. 6 weeks later after more talks about divorce he asked to go again. By this time, everything I had told my therapist, we both though couples therapy really wouldn't do any good until he got help/worked on himself first. Suddenly, he has started helping around the house. Dishes are being done if I don't get to them, vacuuming, and he's being a bit more involved with the kids now. We had a talk this weekend and he said he didn't believe I was going to leave him when I first started talking about divorce, but now he does. He also said he wants to help out now becuase he realizes he should have this whole time. (Though he still has yet to make an appointment for therapy, but frequently brings up that he "should") The problem is, I'm tapped out and have been for months. I don't see a way to trust that his sudden "change" is a permanent thing, and quite frankly I'm angry that he only now, after he realizes I'm serious about leaving, is he willing to try harder. There is so much more to the story, but this just touches on some of it. I feel guilty for wanting out, he keeps telling me I'm going to ruin our children. I wholeheartedly believe we would be great coparents and I think we would actually be better parents and ultimately I think they would be ok, but the thought is still there. I'm terrified of making the wrong decision. But I am so tired of being unhappy. I truly believe my anxiety and depression have escalated over the years with all the built up unhappiness and issues in our marriage, and I'm ready to work on myself. Not to mention the lack of any intimacy has killed my self image. Part of me feels like I should continue to fight for our marriage and figure out a way to love him again, and that if I don't I'm just crazy to throw all these years away. Though, he admits that there really isn't much to turn to because really our marriage has never been that great. Ahhhh. Hellppp.