If you can find a nerite, you're better off with one of those. They are the best algae eaters. Some apple/mystery snails eat plants. o.O Plus they won't breed like apple/mystery snails will. Check your nitrates; they can cause algae. I know hte feeling, have a big problem in my sorority. High nitrates might be why Kei isn't hungry?
Haha, it's always so funny when the bettas get a hold of a wafer. One of my girls is light-colored so I can see the actual wafer in her stomach.
Wood but line the bottom with plexiglass maybe? That way the condensation won't warp the wood.
Put an anubias or a java fern in that corner, if it doesn't get enough light. Or a crypt. Anything that does well with low light.
I hope Kei gets better. :( Poor Kei.