Not to worry
Once you run 2 separate lines and submerge the main line between 1 and 2 inches below the sump level, all will be good
Only thing that happens is a lot of air gurgling when you first fire it up as the air is purged, splashing water everywhere
I solved this by adding a splash guard around my drain lines
Yeah, currently my return in the sump is submerged about 6" in cylindrical acrylic tubes...yet still continuous 2- 3 foot geysers!
I'm sure you are right that once I run the seperate lines and eliminate the air intake my sump should settle down (after startup of course)