You seem to be an expert in this field, which I am not. I was an antenna hobbyist way back when though.
Back in the day when I wanted to tweak my system, I replaced my RG6 cable with RG11 cable. The gain was minimal but I could see the difference. And that was less than a 30' run from the antenna to the wall jack. As far as tweaking goes (and if you're not already using RG11) that will help a little but not a lot.
Either way it sounds like you have a fantastic set up.