Paying a bit towards the food is not enough as he is surely increasing your bills, council tax and wear and tear of the house. Repairs and replacement of damaged, worn stuff is often ignored but adds to the costs.
I bet that being your house you then do most of the cleaning, cooking and carrying of the mental load so paying a bit towards the food is not helping, it’s massively disadvantaging you.
Keeping a rented place that he doesn’t use screams to me that he is keeping his options open. I don’t blame him for that, I have done the same in the past when I was not sure I wanted to join forces with someone, but take this as a clear warning not to start playing the role of a supportive and accommodating wife when he is not keen in reciprocating in efforts and commitment. You are just getting more work and more expenses in exchange of getting an expensive companion who uses your time and resources without given in the same measure.
I would feel tempted to let go of convincing him to leave the flat as it is unlikely the money saved would benefit you as a couple anyway (he would be helping more with the expenses already if he was that kind of person) but mostly, because it will make it easier for you to kick him out when you get tired of being taken advantage of.
Sorry op, but if the above applies, it seems to me you have got a cocklodger there… they do not need to be unemployed, just unfair.