I think the dialogue implies that Leia and Ben may have had an unusually antagonistic relationship for mother and son, not abusive or anything, but something likely to happen when a woman who watched her planet blow up partially under the authority of her own father starts seeing some resemblance in her own kid. And it seems implied that Leia sending Ben to Luke lead to Han leaving Leia; I think that he and Ben may have been closer when Kylo was younger, but that Han "abandoning" the family afterwards really hurt Ben.
Then it sounds like Luke did his best with the kid, but Snoke snuck in and somehow convinced Ben he should idolize Vader, and bam! Kylo Ren is born.
Here is something that occurred to me; Kylo seems to be the only Knight of Ren with a lightsaber, and he appears to have cobbled one roughly together on his own. Since we don't see that Padawan he kills with a lightsaber either, I think Luke put off that portion of Jedi education until later. So he would have focused on Force moves- like Kylo's stun and freeze maneuver, which isn't inherently aggressive or offensive, and in fact seems like the perfect non-lethal move for a Jedi. It's also the only move Kylo seems perfectly trained at, so I think Luke probably focused on that hoping to get Kylo to keep his anger under control with a non-lethal move that would afford him time to calm down.