Factory ammos are quite conservative in the seating depth so it won't easily get jammed
Measure CBTO only makes sense if you hand load. Then measure where the land is in your chamber then back calculate the CBTO based on the jump you want.
Garmin is way more compact and reliable.
Labradar is very affordable now and will be useful to measure the MV down range, in case you need to calculate BC.
I'm using 115 on BTX mostly for the brightness, as BTX splits the light among to eyepieces.
For digiscoping with mirrorless, the best option would be TLS + ATX/STX. That will give you the zoom and reach, then 85 can be a good choice.