I'm not familiar with your interface but I think the echo may be due to latency issues within the interface or software you're using. If this is the case, what you want to do is lower the latency settings to the minimum and hopefully your problem will be solved (assuming it is a latency issue to begin with.)
Concerning the recording on one channel thing, again I'm not familiar with your interface but usually when you don't get a signal you have the wrong button pressed/not pressed (phantom power not engaged when you want to actually record a mic that is powered by it) or some misconfiguration in your mixers (software or hardware) routing configuration.