Is the issue really the prenup, the fairness of the prenup, or the trust you lack between each other? I don't blame the guy for wanting a prenup given his situation - prenups are actually good for both parties (as long as they are spelled out and fair). What's fair? That's up to you to decide. Is it fair for you to get 50% of his stuff if you divorce after 2 years? Will the allure of having 50% ownership in his stuff actually cause a divorce because you want control over your share (you said he wanted to control all spending) and you are suddenly intolerant of all those things you posted on this forum of him doing that pissed you off?
Look at his point of view. He has to protect himself, his business, and his kid from a possible second divorce in his future. He probably senses all of the issues you posted about him, all of those reasons why you are hesitant to marry. If he is half as unsure as you are about the marriage I wouldn't blame him for insisting on a prenup.
Like the other poster stated, you did post asking if it was right to marry for money, and you even said it might be a marriage of convenience, for money reasons. I'm not saying you are a gold digger, but I'm sure he senses your concern for the same money that he has concern for. You said life will be hard for you financially if you leave him, and hard if you divorce after marriage, so why not just get married and take the risk? Either way you said yourself breaking up or divorce would each leave you broke, so your only option of being financially secure is if you get married to him.