About the Gamzee's Dream Self thing, isn't it implied that Gamzee doesn't die in any Timeline, Dream Self or not? The only Timeline where we've seen that happen didn't even become doomed, it was erased from ever being by John's retconning. And the lack of any Gamzee Ghost in the Dream Bubbles (Jadesprite showed to have been in the Bubbles it's to be assumed they have separate ghosts) would indicate it's still. Sort of perhaps drifting in the Furthest Ring? You can't keep the clown down. Sadly.

All ghost Gamzee are in the same place, a bubble separated from all the rest, all of them lying in a great giant horn pile and eating pie.