I think there'd need to be much more to behavior than this to reach a bipolar conclusion, not to say don't pay attention to what's nagging at you , if it were and things patched up, knowing about the illness can save you alot of emotional energy wasted wondering and worrying.
From what I'm reading there's so much seemingly unresolved about his family of origin issues and gosh, something minor to you could have royally set him off, with this cold feet business.
If pointing fingers of blame, he could very well be out of touch with what makes him tick and tock.
And without his dad, there could be something that's weighing on his mind.
Or he's just stubborn?