Where does Kylo ren go from here? He can't be redeemed to the light side or in the audience's eyes after what he does.
sure he can (well, maybe not in the eyes of the audience, heh). It'd make him a much more interesting character, precisely because of his heinous acts. Heck, I bet even Leia is going to forgive him. If he just decided to double-down on evil because he's beyond redemption anyway, that would be kind of boring, no? Also, very Anakin-like. First he has to sink to the lowest lows and be broken before he can rise again and begin to rebuild himself
he voiced doubts about his very own convictions in his conversation with Darth Vader's helmet (yeahhh), Han straight up told him Snoke is just using him for his own ends and will discard him eventually - and it didn't look like he couldn't believe it himself - and then there was the brief conversation with Rey in which he tried to get her to accept him as her teacher, because he clearly sees something in her, perhaps something he is not. The signs are there. I wouldn't really be surprised if he betrays his master in the next movie