temminckii can be a bit on the bossy side. Provided that the individual you keep doesn't have a bad temperament, adding more is feasible. However, given the tank size I would avoid both the pink margin and lineatus. The Scotts is an absolute "must avoid" too. Always use an acclimation box when adding any new ones.
The 3 on your wish-list are fine. Best to add the two Halichoeres at the same time or in near proximity. Slightly safer to add the flasher before them. All together for the three is okay too, if that's your preference. The two fairys your considering could be okay also, but there is aggression risk with the Solon fairy.
Neon dottybacks can be aggressive - but I don't have any experience with them.