You've got to remember this is Long Range "Hunting
" so most guys this time of year are out in the field looking for critters.
I'm not allowed to give out "qualified" information but I'll at least give you my $ 02.00 worth.
You've got the Kestrel and that along with a GPS will give you elevation and all of the data you need for your software. I'd definitely recommend you get the actual velocity for your load. I set my Kestrel to give me station pressure, not corrected pressure and feel that it's far more accurate that way.
Then shoot it for drops and to compare it to your software solution. Then, if necessary you can play with the software to get it to match your drops and then you will be able to rely on the software.
Don't worry about the angled scope base, just measure from the center of the bore line to the center of your scope and you'll be fine. It's not a real critical measurement.