this is what I’m trying to figure out, whether this is his way of dealing with things and if I need to be more understanding?
You're totally missing the point. Which is that yes, this might be his way of dealing with things, but that doesn't make it ok. His behaviour is unacceptable, regardless of the reasons for it.
Him being upset if you leave isn't a reason to stay. He gets something out of this relationship and he'd be sorry to lose that. Him being upset if you left him doesn't mean he loves you. And even if he does love you, love isn't enough, you need respect too and kindness. Not just sometimes, whenever he's feeling ok and you're doing what he wants, but all the time.
Look at what you're giving in the relationship. He's not giving anywhere near the same amount, he's taking. And don't start saying oh but he provides a home, because he'd have to do that anyway for himself. He's not provided you with anything, he's just doing what he wants and letting you tag along, as long as you don't annoy him.
If he can't trust you financially he shouldn't be living with you, because what's the point tying yourself to someone with that level of commitment if you're not a team? For him it's all the benefits of being married without actually being married. You both are well aware he could kick you out without a seconds notice (he makes sure you're aware of that with his horrible comments about psycho, being difficult like his ex etc).
For you this situation is nothing but instability and insecurity, which keeps you slightly nervous about the situation and running around trying to make him happy. You're trying to create stability for yourself by appeasing him. It's a mugs game.