Is Paul mentally ill?
I reckon he might have something wrong with him that's been going on for over thirty years. I know he suffered a lot after Terry shot him and rightly so and he wondered if she really loved him but his behaviour was atrocious and he's always refused to see a counsellor for his problems, and his refusal to visit her in prison which let to her suicide. It's like he's got Jekyll and Hyde syndrome, he can be nice when he wants but he just lets things get on top of him all the time and hits out at people like a spoilt little child when he can't get his own way, A bit like he keeps on this feud with Terese which has been dragging on for months with no end in sight!
He definitely seems like he has some form of depression that has never been looked into and been left unchecked for such a long time, Either that or some kind of personality disorder. It seems like he's inherited Jim's stubborn streak, and although he could be pompous sometimes, he was never nasty or underhanded.
I know it's because the writers want to keep up with the whole "bad guy" act but I just wish there was a 100% proper reason for his weird behaviour!