You got a deresa clam, right? Mine did well with that same lighting in a 72g. But yours is deeper. If it hasn't done poorly in 2 years, you're probably gonna be alright.
There's always leathers. If there are places to put corals halfway up the tank or higher, there maybe more opportunities. Frogspawn was fine on my bottom, so maybe you can too if placed a little higher. Maybe dot the landscape with a couple of ricordias near the top also - one brown/orange, and another green/yellow. MY LFS
sells those for $20 if a single polyp - ususally attached to a very small rock or empty snail shell. I've superglued those to rock ledges succesfully. They'll multiply just like your shrooms
Cladiella/finger leathers is another decent choice for moderate light and current. Capnella leathers (kenya tree) may also work for you.