I'm not an expert, but as far as the one that won't stay under the water goes, I've read that tadpoles sometimes get that problem when they ingest air while feeding. Do you use floating food? The article (wish I could find it again) suggested you could try to prevent the problem by using food that sinks, even though that makes it harder to clean the tank.

Other than that I don't know what to tell you. Good luck I guess.