Sorry I just re read this. For a basement sump you pretty much need to have the drain valves downstairs. What happens is the water drains into the sump and causes water from the sump to be sucked back up into the pipe until that column of water becomes too heavy and dumps back into the sump. this explains the surging you're experiencing. I would try separating the drains, gate valve one of them at the sump so that one is a full syphon with no air intake at all, terminating below the sump water line. That's all I can think of.
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