I think OP is using a Float X2 by the sound of things.
A coil shock with a heavy spring may work – regardless a 500lb spring as suggested would be way too light. According to the shock set up chart here OP will need something like a 650-700lb spring.
Bear in mind though pretty much any bike is going to bottom out on 6ft+ drops etc. but you certainly want to be more around 30% sag.