The power inserter is part of the preamp system. It makes it possible to send the DC power up to the preamp AND send the signals down to the TV on the same coax line.
https://www.channelmaster.com/TV_Ant..._p/cm-7777.htm
manual
http://downloads.channelmaster.com/S...77_7778_UG.pdf

http://forum.tvfool.com/attachment.p...1&d=1496676770

http://forum.tvfool.com/attachment.p...1&d=1496676876

Yes, it can make a big difference. Old coax can go bad from corrosion. It could be the reason why your neighbors are doing better than you are.
It might make it possible to receive WQPX, but it will never be 100%. Just an experiment, no guarantee.

Try the new coax first.

I have new coax laying around, I may try that today. As for the power inserter, yes I have that, came with the cm-7777.

Just an observation. It might be costly and time consuming
to TRY and receive WQPX and it might never happen reliably,
if at all. According to Wikipedia, there are six subchannels,
most of which aren't anything special. You might be better
off just streaming a few additional programs to your current
tv......

Yeah I was looking at that too but I want to try to get the absolute best reception I can get..... its a challenge now. Plus by getting that one channel I also pick up channel 31 which is 3 more channels.

Maybe, it's not possible to accurately predict what will or won't be received with signal estimates as low as yours.

All you can do is try it and see what happens.