I think you've gotten some great advice and food for thought here.
This relationship seems to be out-of-balance. If he truly wanted a life with you, he'd be moving Heaven and Earth to make it happen. With all that he expects you to sacrifice, he'd be doing his best to make your sacrifices worth it. He would take whatever work he could find to get things situated for the two of you to start your life together.
Instead, a 37-year-old male is sitting in Mummy's house, eating her food, using her internet and snubbing "boring" jobs. Even a "boring" job would help provide the means to set things up for your arrival. I understand needing you to work as soon as possible, but when is he going to work?
Would you move to the UK if he weren't in the picture? What would you do if you got there and he didn't change his current ways? If you decided that the move was a mistake, how easily could you return to the US? Would you be happy supporting him while he hung around at Mummy's all day? It sounds like you've got a lot to offer, but it sounds like it is not reciprocated.
Sweetpeach made some excellent points about his and his mom's relationship. If he's always been the apple of her eye, your arrival will upset the apple cart. You and Mummy could end up competing for his attention. What would you do, if you moved in with them, and Mummy suddenly decided you had to go--right this minute?
Bottom line, he needs to show he's as committed to making this work as you are. His changing "plans" (all of which seem to have you getting an income a.s.a.p. as a main feature) aren't enough. He needs to get a "boring" job or two if that's what it takes to start your life together in the UK. He needs to look at places, other than Mummy's, for you to live as a couple. This situation has a lot of red flags in it. I do wish you lots of luck, wisdom and peace, whatever you decide.