Just replaced my sump pump - couple of questions

I just recently replaced my old pedestal pump with a Zoeller M53. I've got a couple questions if someone could answer.

1)Even though the paperwork said that 50 series pumps come with a drilled vent hole in the housing, (which mine has) it would be a good idea to drill a 3/16" vent hole in the discharge pipe somewhere below the check valve and somewhere below the sump pit top. well, I drilled one about an inch above the pump housing where the discharge line connects. needless to say, after the pump draws the water down below that point, it SHOOTS out of there all over the place. so, I put a screw in it to close it up. question: was it really necessary to drill that hole in the first place? why does it need a vent hole anyhow?

2) there is about 9 feet of discharge pipe upwards from the pump before it turns and exits the house. The check valve is located about 4 feet or so above the pump, so about in the middle or so. Anyhow, every time the pump shuts off, whatever water remaining in the pipe above the check valve comes down and bounces on the check valve, sort of like water hammer effect. it's loud, it goes LUG LUG LUG LUG LUG.
question: should I locate the check valve closer to the pipe exit?

Thanks in advance.

The hole is to prevent the pump impeller from ever becoming airlocked. On mine, I made a splash shield around the hole using a zip tie and a piece of plastic from a milk jug.

The check valve you have is the problem.
While it should be lower (in the pit is fine), what you want is a "silent check valve".
A.Y. McDonald makes silent PVC check valves that I have been very happy with.

Thank you very much! that answered both of my questions!