A few thoughts ...

1) a LR rifle is never good as a “do all”. They’re specialty tools.

2) the Elite 3500 you have is a scope with good glass for the money.

3) a $500 budget for a 1000 yd scope is not enough budget. You need to double your budget.

4) the FOV At 6x isn’t going to be very useable at 15 yards (not to mention parallax ... even with side focus adjustment).

5) for LR shooting you will want the max magnification Ana this will be more true as you grow older. I know a 1000 yard shooter personally who uses a fixed 45x on his rifle. He’s nearly 60 years old.

I’d scrub your project or reconsider the “do all” or “$500”.