if you really want him to be your boyfriend,
why dont you just directly tell him what do you want!?
if you like each other, that's easy to get together!
dont be shy and get what you want!
but for me, i think 暖昧is quite good that you two wont break.
also, you two wont argue with each other and it can keep your relationship better then you two get together.
this is from my own experince, hope that it helps.