I was always really confused by the evilness of Slayer. Obviously he has always been evil within the timeframe of the novels, but Luc's history (and also judging from his more high profile relatives like Tigraine, Rand, and Galad) never gave me the impression that he was evil pre-Slayer. And Isam's only connection to the Shadow comes from the mistake/bitchiness of his mother and I never felt that Jordan was a real "Sins of the father pass onto the son" kind of guy. In my mind, I always felt that something DO-related happened in the Blight that turned them evil. Maybe they unknowingly wandered to Shayol Ghul and got corrupted by the proximity to the DO. I don't know, but nothing from their back stories explains why they are evil so I have to assume it's not "natural" to them.

It's already been proven that threads can be put back into the Pattern. That's the whole point of reincarnation: one thread returning time and time again to life. It has so far simply been limited to natural rebirth, just as healing stilling had never been done before Nynaeve, even in the AoL. Nynaeve has a semi-strong grasp (at least compared to her contemporaries) on TaR, where all the spirits remain unseen when they're dead and has access to way more knowledge through Birgitte and possibly Perrin's wolves.

As for the "die and live again" TaR argument, I agree. The soul of the Dragon was confirmed to live there between lives when Hawkwing recognized him at Falme, so that seems to indicate that that's where he'll go when he dies. Plus, as a connecting world to all others and given that the Dark One (and his prison) is in all the world's simultaneously, if Rand wanted to completely seal the Bore in all worlds, he would have to seal it in TaR.

What about Lan dying and having Nynaeve and Rand working together with a sa'angreal (guess it would have to be Callandor plus one other. My guess would be Moiraine) to bring him back to life. Both have been linked to healing death, first Rand with the little girl in the Stone of Tear (tSR, I think? Maybe the end of tDR?) and Nynaeve has repeatedly said that anything should be healable. She already proved one "impossible" thing possible in healing stilling, so this could be done too. They could possibly throw in Damer Flinn and make it a much larger circle to grant way more of the Power. Something like this would obviously need a LOT of Power. They also both have deep connections to Lan. Rand sees (possibly should be past tense) Lan as a psuedo-father figure, learning everything he knows about the world outside of Emond's Field from him. I don't think I have to explain Nynaeve's connection with him. With Tarwin's Gap coming and Lan's drive to die, I think he will probably end up dead, but like Rand, that won't be the end of him.