Do you know when it's time to give up?

Like so many of the posters on here I am the sad, frustrated, resentful spouse of a husband with ADD. We are currently seeing a marriage counselor at my suggestion because I found myself reacting to my husband with less and less patience and fantasizing about getting out of my marriage. It just seems like life can be complicated enough without the added daily stress of job loss, money, unfinished projects, depression, mood swings, etc. My husband and I got married relatively young (25) and we have been married for almost four years. Before we got married I guess I knew that he had ADD but it didn't seem like a big deal. He had a decent job and an apartment and money in the bank. He paid his bills and shopped for groceries and cooked his own food. But after we got married he started to go downhill. Though he is a talented writer he has struggled at every job he's had. Basically he can't keep up with the workoad and stick to deadlines. This has led to him being fired twice. Now he's doing freelance work out of our home office, which has been pretty much a complete disaster. He has no self control or ability to make himself work. Especially when I'm not hovering nearby to make sure he's working. I guess my big problem is that he never seems to try to make any real changes. He says he tries but that his brain is broken. I understand that it's a LOT harder for him than the average person but in my opinion he hasn't yet given it his all. He stopped taking his depression meds because they were making him groggy (didn't discuss this with his dr.), rarely takes his Adderall because sometimes it doesn't work (I don't get this!). At my suggestion about a year ago he started seeing a psychologist who specializes in ADD. He went to her a few times but then got let go from his job so he figured there was no point in continuing to go. I have encouraged him to see her again to see if she can help him come up with some coping strategies and brainstorm about employment options but he hasn't picked up the phone. I should also add that our marriage counselor has encouraged him to see his dr. and the therapist and to think about meds as part of his overall treatment plan. He agrees while we are with the marriage counselor but hasn't followed up in any way. We've had serious conversations where I have told him how unhappy I am being the one who is bearing the weight of everything. Budgeting, paying bills, cleaning, cooking, grocery shopping and being the primary breadwinner. I can't even imagine if we had kids like many of the others on this forum. I would love to have kids but I refuse to bring them into this world until/unless our relationship improves. I feel like I have begged, pleaded, cried, yelled to get his attention but it never works . . . or never works for long. If I get mad, I'm the bad guy because I'm not supportive, if I get sad it makes him feel worse about himself. Basically I feel like there is nothing more I can do. I've tried so hard to help him: finding therapists for him, buying him books (both Driven To and Delivered From Distraction), printing out articles about tips, coping strategies, etc. for dealing with ADD, checking in to make sure he's doing his projects (he never is), encouraging him to exercise with me, take his meds, etc. Honestly, he should've been doing many of these things for himself, but he didn't, so I did. It's pretty much the way our relationship works - he doesn't do what he is supposed to do so I swoop in and try to keep things from falling apart. I'm sick of it. I want an equal (ok, halfway equal?) partner. At some point I have to cut my losses and move on if he isn't capable of making any changes. I'm not asking for a perfect husband . . . just an improvement. I feel like I've given so much and tried so hard to help him and it hasn't made any difference at all. This relationship has taken so much out of me and the return just does not seem worth it some days.