If you’re always dead-nuts center, you won’t have parallax error. I didn’t double check that calculator, but it should be error based on max offset.
Shooting big game out to 500 yards means your shooting about 2-3 MOA targets, which is pretty big. You can screw up and still hit those big targets. You should be able to use a fixed parallax scope to shoot big targets at that distance.
That said, you’re getting taken advantage of to pay $900 for a scope without adjustable parallax in 2021.
You have a whole lot of threads going about this SHV, but I’ll give you some advice that wasn’t requested in this particular thread: you can’t upgrade scopes, but you can upgrade your rifle. You have a $2500 rifle, and you’re looking at a $900 scope. Those priorities are backwards. Sell your rifle, pickup a $2000 - $2500 scope, and pick up a $700 factory rifle. You’ll be way ahead of most.