Money inequalities can also set up a power dynamic for the future that you probably don't want, with him using the money issue against you...
For the present, if he is expected in the relationship to pay for the majority of dinners/etc., and he's not down with that arrangement (or he was, but now that you've been together for a while he wants to equalize it), then seems like he is getting resentful but doesn't know how to communicate that except with half-jokes.
How's your communication? Can you say to him, let's talk about money and expectations, and have an honest conversation about it? Because it seems like there are valid reasons for him to pay more (he's more established, has more money coming in than you) and also valid reasons for him to be getting resentful (if you've always assumed he'd pay the bulk of it, but never actually decided that with him). If you're looking at trying for a long term relationship, being able to iron out little resentments like this (as well as big topics like how to work with money in the relationship) as they come up is a good habit to form.