If you already have a 20 MOA base, why would you add another 20 MOA using your Burris inserts (like you describe?). As of now, you have 40 MOA of cant, and this is why your NF is close to bottom on the elevation. Do you really need all this elevation adjustment? Are you shooting out to 2000 yds?
If your windage adjustment on scope is way right, yet your zeroed, you will need to adjust inserts to "aim" your scope further left (thick side of insert right side of ring, thin side of insert left side of ring). If you do both fore and aft rings (with your 0.010" inserts), this will free up 20 MOA and bring your scope's windage closer to mechanical zero. If you do either front, or rear (i.e. not both) your looking at a 10 MOA adjustment.
To start, I would bring back your windage to mechanical zero. If it's 80 MOA for example, set it in the middle at 40 MOA. Then go to the range and see how many inches LEFT of a large target your POI is. Then adjust your inserts accordingly as per above (20 or 10 MOA). Btw, you can order other inserts that give you 20 MOA per ring, so using on both fore and aft ring you can adjust up to 40 MOA. I had to adjust a muzzleloader of mine 30 MOA scope tilt upwards (i.e. opposite direction of your 20 MOA base) as my elevation was bottomed out (60 MOA scope).
I think above is correct, please let me know if I got it backwards.