1. Dunno, don't remember. Fine with removing it, if nothing else, if I find something that suggests it in 2027 when I revise the profiles, I can just re-add it. I didn't include scans of all my findings so I try not to get snagged on all of these things.
2. We use whichever is higher- if a CR 5 is stated to be an 8th level caster, we acknowledge that they are 8th level and thus scale to 8th levels. If their CR is above their level, then they have something placing them above that level and we use CR. So, CR 15. Both are Low 7-B, so the rating remains the same in either case.
3. As far as I can tell, Wave is a halberd that featured in Baldur's Gate 2 and had a strong connection to water elementals. No sources mention it based on the wiki, so... probably never used again.
4.
I believe you're talking about these guys, good sources can be found at the bottom of most Forgotten Realms Wiki pages (hells be upon you if you want something non-FR related, ahem Iggwilv ahem).
5. We don't normally, no, unless we're given a list of abilities he would otherwise prepare (or in a Wizard's case, what other spells are in their book). What he has per the statblocks is considered standard loadout. If you wanted to say "possibly many others" and elaborate that out of character, he
could have a vastly different array of powers, I don't see the harm in that and we've done it for pages before.
6. Organic Manipulation, maybe?
I was looking on the Dnd resistances page, and I'm pretty sure the
damage transferal ability that's listed (life drain) isn't how damage transferal works on the wiki.
I think it fits this bit:
"The ability can also be used to have the target such as an object or person take damage for the user or have the target suffer the same damage they have suffered."
...in that the target takes damage which then heals the caster (or some other target). The effect is functionally, mechanically equal.