1/2 MOA is plenty good enough for big game hunting at reasonable distances (400 to 500 yards, maybe further.) I think the 100 grain Sierra is fine for antelope; for deer and elk I'd probably be looking for something a bit stouter.

Once you decide on a load, then you need to do some actual shooting at longer distances to see how the balistics really perform compared to software estimates.
Sounds like you're on a fun journey.