Can Nick still be redeemed? Of course. Even with all the horrible stuff he's done, it's all been on drugs. He can kick the habit and get his life back together. A sincere, unqualified mea culpa and putting himself in rehab would go a long way.
Will he be redeemed? From all the information we have so far, there's absolutely no indication. He hasn't owned anything. He's blamed everyone else, deflected, lied and basically said he's going to keep doing what he wants for the foreseeable feature. What he should be doing right now is getting on his hands and knees, crying his heart out and apologizing to everyone for all the horrible things he's done to his friends and family. He should be begging for forgiveness and admitting what he's done is the most horrible thing he could do, and he never wants to be this person again.
Instead, he's doing the typical crackhead thing where he won't admit to anything, even when he's caught red-handed. He thinks he can be a good parent and still snort coke and down booze. He won't admit he has a problem, and can't even start to fix it.