Personally, I'd suck it up and get the sale done, working hard to make the price as front-loaded as possible. Depending on the buyers appetite for you to keep working there you could:
A) Suggest that you're excited to stay with the business, but if they feel there'd be too many chefs in the kitchen and that you should phase out, you'd like to know about that now... i.e. open the door for them to express how critical you are to the deal.
B) If they DO really want you, push hard for a front-loaded deal (i.e. initial payout versus earn out) and then give notice 6 months after the deal closes. You'll leave some (maybe lots) of $ on the table, but who cares. Selling a company isn't indentured servitude. Someone else owning the company might relieve some stress. If it doesn't, punt.
Broadly-- I'm a believer that happiness is generally internal. If you can't find a way to be happy with this job, I suspect you'll have a hard time with a different one. Starting ASAP, I'd make some changes to see if it makes a difference. Get therapy. Try anti-depressants. Shut off your phone at 6pm and don't open your computer. The sky won't fall. Exercise. Meditate. Try psychedelic mushrooms (only half kidding-- there are some studies that one dose positively impacts depression and anxiety). Eat better. Go into work late AM twice a week so you can take a long walk with your wife. Schedule vacations. Go into the woods a lot (exposure to green space helps depression too). I just read that doing tai chi helps with depression. Schedule weekly lunches with friends.