Splitting divorce now might be just what you need, but you will probably have to pay through the nose to in the financial settlement stage. It might be worth it, but it might not.
Because after 20 years of marriage, the DH could argue to the courts that he has been Primary caregiver to school age children, doing school runs and has supported the OP’s career so she could work away from home at times.
Furthermore, that he is disabled by a long term mental health condition which precluded him from being employed for 9 years. The usual process for patients in recovery after a long term mental illness is to ease back into work with support by exploring part time volunteering, studying new qualifications, moving on to part time paid work, and then to full time paid work. No agency is going to say that a person who’s suffered terrible depression for 9 years can just jump into full time work without very high risk of a relapse.
So he argues to the courts, I was essentially a disabled SAHP, we have been married 20yrs. He will ask for 50/50 of the assets and he won’t have to pay CMS, how can he when he is disabled and earns nothing? OP may end up losing half of everything, including her pension.
I’m not saying this is my opinion. This is just what the DH could argue. I’m saying this as a devils advocate.
So I’d get legal advice in all honesty because it might be worth pushing him to get back on his feet through that Richmond fellowship service and then divorcing because then the courts would be less likely to listen to a sob story if he’s recovered and working.