I'm 39 and disabled in addition to being politically exposed (that is, a bunch of people whom I've never met know me by my real name and, for reasons so silly it is not worth getting into, utterly hate me) so I have some insight into your situation.
To start: this utterly sucks. If it makes you feel better, it's not as uncommon as people want to believe. It awaits probably half of the people here in middle age (meaning 40s and 50s) due to a mix of random bad luck and work stress. Unfortunately, there's no easy fix. Getting sick invariably damages your life, in our society, more than it should. Money problems are an absolute nightmare that cannot be understood except by people who have experienced them.
It is truly astonishing, in the United States, how quickly your life can turn to shit, and how readily our society will let it happen. If the 99 percent of people who will not inherit high positions in the corporate system realized this--if they realized that they are not protected by their educational paperwork or "professional network" (which will disappear as soon as they need it)--then our entire society would be overthrown (good riddance) in a few nights.
It's good that you have family you can live on, and you shouldn't be ashamed of the fact that you're in this situation, because it's not your fault (shame or guilt will just make it worse). Not everyone has that. I'm not saying that to make you feel bad about people who are worse off; I'm just stating a fact. People have come back from worse.. although the path is difficult and the odds are poor.
What happened with your consulting clients? Did you inform them of your situation, and were they understanding? Would you be able to use them as references? (If they say anything bad about you, you can argue that they're engaging in discriminatory communication and sue their dicks off... but, ideally, things would be in a state where they'd say good things.) Why wouldn't they have been accepting of your scaling down your hours?
The first thing you have to do is focus on your health, like nothing else matters. Easier said than done, I know. If you can improve your situation to the point where you can work 25, then 30, then 35 hours per week... then great. It might take a few years, though; health problems do not resolve quickly, especially later in life, and doubly-especially when bullshit survival pressures do not let up.
I think you and the corporate world are, to be frank about it, probably done. For all the claptrap about corporate "mission", the truth (that everyone knows but cannot speak) is that the work has no real purpose and it's all about the money (and ego and narcissism, but those are connected to the money and the ability to get it). When you become disabled, you're no longer in the running for the executive-level jobs that are the carrots dangled in front of the masses, and everyone knows it. So, the cunts up top will take your inability to work 70+ hours per week as an "attitude" problem rather than a justifiable concession to a hard medical need. You can draw out the process, document everything, and probably collect a better-than-typical severance when they eventually fire you... but I'm guessing this isn't the way you want to live. With or without severance (which is never enough, even if you played the disability endgame like a pro) getting fired every year still fucking sucks.
You could look at government jobs. There are a lot of jobs in the public sector that are "boring"--meaning there's a fair amount of bureaucracy, and you're not going to be flown to Hawaii after a product launch--but that will allow you to work from home, and scale back to part-time if/when you need to do so. (I'm guessing that your disability fluctuates, and there are times when you can work 40+ hours and times when not.) You're not going to make a ton of money, but (let's be honest) that's never going to happen for you (unless your disability spontaneously resolves, which I hope it does, but which can't be bet upon) in the corporate world either. Plus, while some government jobs are bureaucratic waste, there are a good number of them that actually serve useful social purposes, and give you something to think about other than your health.
The best strategy, if you can get it to work, is probably to find a "boring" (boring is good, because income is a utility and having it turned off fucking sucks) job with flexible hours where you can work from home. You'll need one with good medical benefits, too. The era in which you can bet your life on a dodgy startup (it didn't pan out the last time) is over.
Good luck! You are certainly not alone in this. Infirmity happens to all of us; the only variation is in when it comes.