I have gone through this befor with a basement sump. I also have the same pump as you and hose size .
There's not a big difference in our set-ups. My horizontal run is 16'.
The most critical part for basement sump is all that horizontal laying pipe slowing
down the inertia of flow.
I have found that creating a angled as oppossed to a true horizontal run was the key to getting the air forced out of the siphon line , the other lines were all left horizontal.
In this pic you see the sipon line up higher then the rest of the lines
From the top of the truss I just shimmed the return line to create a angle until I was at the bottom of the truss.
Oh ps. the small drilled hole is ment to be just above the waterline when the sump is at running level, this reduces the pressure at the end of the hose which allows the air to purge.