I dunno about that, he seems to genuinely like Sadie and damn, I forgot her name, she's the daughter of fish pizza but then again one girl is basically unobtainable to him and he doesn't treat Sadie all that great. I always liked the role reversal dynamic in the Sadie/Lars relationship. She's very strong and independent and Lars is definitely not and anything is possible in Steven Universe.
I agree with you about the Steven/Lars fusion theory. Steven is all about the defense, when he's Stevonnie with Connie, the fighting ability is all hers