I'd pay for repairs/purchase something I was using and contributing to the wear or tear on within reason, i.e. such as a new appliance. If you were about to put the house on the market to move somewhere together and doing things like painting and decorating or carpets etc in order to sell, I'd contribute to that too.
Big kitchen renovation to a house I didn't own? Nope.
Did you ask him why he doesn't want to move now, if you're planning on moving in together in the future anyway? If you for example said, let's get this place smartened up so we can buy a new and bigger place now and get the kitchen we want in the new place I'd be curious how he responded. If it's no, it's got to be here because of location xyz, tell him great, let's take steps to get me on the deeds now etc, we'll upgrade here and then see how we feel later. You'd basically be buying into his place. I can understand he might want so contribution to that, allowing however for what you've paid in rent. You need to think of a sensible number.
This is not a cheeky request and does not make you a tightwad.
If his reaction is totally negative I would assume whatever plans he's mentioned re moving/buying a place with you are at least three to five years away. Is that your timescale? And this is a somewhat generous assumption; he could not be sure he sees a future with you and feels since you're living there it's fair to ask because you 'benefit' from using the house. It shouldn't work like that, a new kitchen is a huge investment.
Also this from @Ileflottante If you’re worried he’ll break up with you for not pouring your own money into his house, then all the more reason not to.