Swapping cranks on SRAM Force AXS eTAP
They look to be compatible. The website says they'll work with any road DUB BB, which you have. Changing the spider shouldn't be too difficult as long as you follow the video. You can also find more info on the SRAM Service website. For example, here's the spider and chainring installation guide.
Here's the DUB BB compatibility manual: DUB™
MTB and Road
Cranksets and Bottom Brackets
As for the big 50Nm bolt, either take it to a bike shop or even a car garage and ask to borrow their torque wrench (&quot;It's just one bolt, can't I just use it for a quick second!&quot;), or just guesstimate the torque, perhaps with the help of a little math to find the amount of force needed with your own wrench. As long as it's on pretty dang tight, it shouldn't fall off.