I use 3 of them. One comes in at the bottom, the other 2 I have running in at the top. You are right, the top inlet was for washing only in a dairy application. I prefer the top and assume I get a wee bit more vacuum transfer. (less restriction).
As far as the air leaking, new seals should do the trick. If the glass is chipped a little, then it probably won't help much. In that case, I smear the top, inside and out liberally with vaseline. put the top back on and then smear the outside of the seal/jar with more. Hasn't failed yet.
John Deere 4000, 830, and 420 crawler
1400 taps, 600 gph CDL RO, 4x12 wood-fired Leader, forced air and preheater. 400 gallon Sap-O-Matic vacuum gathering tank, PTO powered. 10 bulk tanks.