RE: Pressure signs this early??????
Honestly, I think your overthinking this way too much without doing some of your own homework. Unless you took your gun to nosler and they personally meausred your thoat, your advise from them is about what you paid for it. There is no shortcut for this stuff. You got to do it yourself on your gun. Its not hard, and important you know how to find distance to the lands if you stay in the reloading world. I took my gauges around 4 gun stores once and measured distance to the lands with 3 marked bullets in 300RUM. I got measurements from 3.66" to 3.90". Noslers test was on there guns. Thats the reason thier "accurate" load is 90% of the time not the "accurate" load.
I mean, are you looking for any other pressure signs? Hard bolt lift? Extractor marks? Case head expansion? Well over velocity? It doesn't sound like you ever went back to try find the following? If you have trouble with TSX, your going to have trouble with 165gr partition.