You can lead a horse to water..

Have you expressed how important this is to you? And if so, he is still not willing to put in the effort? I feel I must be blatant here: Being a dominant is difficult. It's not for people who are lazy; it takes work and dedication. I am fearful that you are simply putting your kink onto your significant other, and if that is the case, then I don't know that it's possible to prevent topping from the bottom.