its pretty clear in the pictures that the pipe is already as short as you'd ever want it.
I agree that the pics seem to indicate a rather long horizontal run... it may be enough to pressurize the line enough that its acting just like a drain that is plumbed too deep.
I concur that the 90 degree elbows should not be there. It's the only thing that makes sense in that both the full siphon and the open drain are not flowing.
Is the open drain air vent going underwater? If so, don't do that.
Is everything working properly with you vent the siphon manually? You said it works - but is it working well?
finally, is the emergency drain going siphon to keep up when you don't vent it? Or, is the emergency drain keeping up with the flow and still sucking in air?