1. I think he should first get a proper redemption and then perhaps go to StarClan.
2. Yes, he's interesting.
3. For sure.
When I first heard about Snowtuft helping the TBC protagonists in TPoNS, I was on the "Snowtuft is a cinnamon roll and is now completely trustworthy" train before actually reading TPoNS and seeing some of the things he still believes in and says.
Here are a few of his quotes:
About Tigerstar I and Firestar
"Oh, I knew Tigerstar! He was a great cat. He could have been leader of the whole forest if it hadn't been for that stupid kittypet Firestar."
―Snowtuft reflecting on Tigerstar to Shadowsight in The Place of No Stars (book), page 143
About his past
"I don't remember much about my life. I vaguely remember I wasn't the nicest cat. Well, if I had been, I wouldn't have ended up here, would I? When I was alive, I know I cared a lot about power. But what does that power mean now? Nothing. When you spend forever slinking through a dark and dying forest, alone, you realize how little power you ever had."
―Snowtuft to Shadowsight about his past in The Place of No Stars (book), page 144
About his current situation
"It's closer now than it was the other day. And this isn't the only place where it's happening. It's like the fog is rolling in from all sides—it's making the Dark Forest smaller. I need help. I know I wasn't the best cat when I was alive. All of us Dark Forest cats have done things we shouldn't have. That's why we're here. But surely I have the right to exist? Something is destroying my home, and I don't understand why."
―Snowtuft on the Dark Forest's situation as a result of Ashfur's interference in The Place of No Stars (book), page 146
About his possible redemption
"When the Dark Forest starting shrinking, I just felt resigned. I thought that maybe everything was going to disappear forever, and that I and the other cats who ended up here would just disappear along with it. [...] You'd think so, but no, I wasn't...not really. I've always believed I deserved to be here because...well, why else would I be here. I must have done some bad things when I was alive. Things that earned my place here. I've always felt that my story was going to end badly. [...] Maybe. Anyway, right when the forest starts to shrink, here come some good cats: Shadowsight, and you Rootspring, and now Bramblestar. Good cats in need of help. Maybe that's a sign that my last actions before I fade away ought to be good ones."
— Snowtuft to Rootspring and Bramblestar about wanting to redeem himself in The Place of No Stars, page 262-263