Awesome! You don't need to wait for the skimmer, you can set it up and use the skimmer after it cycles or maybe even later (don't even need a skimmer if you're willing to do more frequent water changes). The lionfish is going to eat everything that fits in it's mouth so a lot of those fish would be its lunch
! I think you should just stick with the peaceful fish (except the maroon clown can get pretty aggressive, but it's fine for now). The scooter blenny is actually a dragonet, so they are docile and require special feeding needs. So I'd say other than the lionfish and the scooter blenny, everything looks fine.