does the mc get any emotional development at all or is he just consistently an asshole?

The upcoming arc is about him becoming a bit more of an asshole than usual haha.

But he does, towards the end I'd say, but not a whole lot. He becomes bit more attached to his group and manages to make one of them as a really close friend(it's a girl so even more cool). Just before the final arc, we see him actually be emotional again with regards to what happened in the first timeline. The asshole part remains towards the one he considers enemies.