Coralline will grow (and seems to thrive) in pretty low light. My best coralline growth is down low in my tank. The worst is high up in my tank.
Agree that it's tough to kill mushrooms. No need to feed them though - they'll get what they need from the water and lighting. Zoanthids, leathers, and many of the euphyllia species (torch, frogspawn, hammer) are also pretty easy to maintain corals. Sounds like once you get your new fixture, you'll be able to put anything in your tank.
Just be aware that anemones are not really "easy" corals and 4 months is still a pretty "new" tank for them. I know I'm probably just repeating what you've already heard a million times. Also be aware that anemones can and will roam your tank and if it's filled with corals you might lose some if the anemone decides it'd rather live where one of your coral lives.
Regarding water parameters, sg
of 1.024-1.026 would be good as well as calcium above 380 and alkalinity between 8-12 dkH
. Temperature should be stable and somewhere between 77 and 80. Nitrates below 10, but honestly they should be as close to zero as possible. Phosphates below 0.03, but again... they should be as close to zero as possible.