I would go with the stuff higher up...
It sounds like he is getting over stressed trying to stay afloat and all the load from 3 jobs is putting too much strain on him. It can be hard enough to do well in a single job, then add another 2 with their various facets and goals...
It sounds like he needs a good sit down, maybe with a small amount of drink... loosen him up to talk, but not so you are holding his hair back over the toilet again...
Find out what he wants or wanted to achieve but feels he has failed at. He cant become a success in business while trying to do 3 seperate jobs. You didn't mention his age I believe?
If he has reached certain hallmarks like 30 etc then he may well be looking at what he has managed and missing something he really wanted before.
As to how he would go about trying to get that goal... well he may need to look at rebalancing most of his life, if he needs 3 jobs just to stay in the black then what is eating all his capital? Can he cut that back while he attempts to shift from his mass of jobs into a singular well paying job to reach what he desires? Or to fit in further training/qualifications to get to his goal?
It might even be a form of "Keeping up with the Jones." Wherein he is trying harder and harder to match or be better then others he works with, but sees himself as not matching up and being a failure in that form.
There are a whole mess of things that could be leading to his current state and the only way to figure it out is a good long chat with someone he feels able to open up to. Whether he will do that with you as family, yet a relative stranger, so someone he may not have been lying to as much as others... sometimes we will hide things the strongest from those we are closest to and the longer it has been hidden, the harder it can be to open up and admit they hid these aspects from someone they love.
Or they may need that same love in order to open up enough to really go into full depth of their issues.
I lean to the stranger route for some reason I just talk more easily to someone who doesn't know me. No idea why. See which way it goes with him.
TL

R He has some underlying issue which the drink brought to the surface. He really needs a good talk and to examine what he wants from life and how best to reach that. And what changes might help manage it. Whether you can help enough without much of a bond with him is questionable. This could be a time to rekindle and form a bond as brothers, or you may want to pass things along to a family member who he does get on well with but may have hidden his doubts from previously. Good luck either way.