Hi Teabay . I really feel for you. With my previous ex (EA) I lost all my confidence at work (managerial position) ended up on long term sick leave and eventually resigned. It took leaving him and nearly a year of CBT before I could consider anything, even voluntary work.
The first thing that struck me in your post was the timescales. Only a few months absence after 22 years is quite something, and it's only been 3 weeks since you returned. So you clearly have a phenomenal track record as regards staying power. The fact the place has gone down the pan without you also speaks volumes.
Who was in charge when you were off? Why have they done such a poor job that you've come back to a mess and complaining staff? Are any of the complainers at fault, should they have been more responsible/acted differently when you were away?
It's also interesting that nobody knows why you were off, and what you've been/are going through. I can imagine there are lots of possible reasons for this; wanting to maintain your privacy, not feeling that close to your colleagues, feeling your management wouldn't approve. Do you think it would make it easier if your (or some of your) colleagues knew a little of what was happening? If only so they knew that you might need to deal with things a bit differently for a while.
As for the non management role. If this could be for the short term, and financially and career wise you feel it's doable, then go for it. I look back at the times I struggled on when I should have called it quits much earlier. There are no medals, and everyone can be replaced, so do what's best for you. Even if it becomes a long term move so be it, if that's the best thing to help you rebuild your life.
The job I do now is something I chose because it's low stress. I'm self employed and have a lot of control over my day. It's not a job I'd have chosen before, but it's allowed me to recover, care for my dc, and it fits in with my life as it is at present.
As for the anti-depressants. I took some for a few weeks many years ago (see EA above!!), probably not long enough to have any effect. I was scared to take them too, so stopped. I'm sure somebody else will have some advice in this area.