The first and foremost question to be answered is this- is he seeing someone else? If the answer to this is yes, please leave yesterday.
If the answer is no, then ask if he is using drugs/alcohol. If yes, then leave.
If the answer is no, then the two of you need to get into counseling. He is doing everything he can to make his business successful. The relationship between the two of you deserves no less. If he is unwilling to work on this, well---
What you describe is quite a "normal" reaction to stress. I hope the best for the both of you and I wish you well.
Jay