Agreed ^ ^. Approximate sizes, of atleast the bichir and the oscar, and I would avoid keeping the bichir and the pleco together unless they have alot of space, their own caves, etc. But you can try, just watch for the pleco to start "sucking" on the bichir. This is just stressful to your bichir, at that point I would send the pleco on a raft down to visit the porcelain god.
They don't have the best eyesight in the fish world. It will take a bit of time to learn the tank, then the running into the glass should stop.
I honestly don't see a problem with the pleco and bichir being together since its in a large tank and they are the only bottom dwellers in the tank.
Except they love the slime coat so much that they would chase the bichirs all around the tank to get it.
Not to mention a common pleco can easily outgrow his tank.