My butch and I are both lesbians. We are, neither of us, men.
But I call him my boyfriend. I call him my boytoy, my boy, sir, Mr., guy. Cause this language makes him happy. It supports his gender and expression, and it makes him happy.
Butches of all flavors and types have been using he/him pronouns and masculine language forever. Butches have been called boy, guy, boyfriend. Butches have used "traditionally masculine" names like Mitch, Ed, Mac, Joe.
Language is fake! It's all made up! If it makes you happy, use it! Wanna call yourself "boy," even if you're not a man? Do it! Wanna be called "boyfriend," even if you're not a guy? Go for it!