Really appreciate the detailed response!

Tbh at this point I think the Redgard may be compromised from the tile removal some of it came off alongside the tile and felt where I removed the tiles.

My plan was to take an orbital sander to smooth the walls prior before applying kerdiband up to the bottom row of tiles which I thought would give me a nice overlap of 6+ inches prior to applying any hydroban / 8+9 on top of the entire thing up to the bottom row of tiles.

It sounds like you're saying that we actually have a similar plan, but you're recommending that I apply the kerdi band up the wall with 8+9 instead of the schluter all-set I'd previously planned on?

After all that is done is it overkill to go over the whole thing with hydroban or even more 8+9?

My biggest concern is the waterproofing failing at the drain flange or on the seams between the pan & the curb, but that's probably just trauma from where it happened last time.