interesting, without knowing too much it sounds more like anger issues that have manifested into a drinking problem, of course im far from qualified to speak on the matter, other then life experience with alot of these style issues, so take my opinion for what its worth, which is a grain of salt, but id like to hear more about the mood changes, how quickly and severly they change? and what sort of mood changes? we talking gleefully happy to misrablely depressed? or normal to psychotic?
also it might be an idea to consult your local gp, they can give you more info on signs you should look for, so you can make a much more informed decision on the likely hood of him being bi polar