I cannot give you a specific setup to run, but here are my initial thoughts...
The only way to fix traction/bite is with a track (not an option).
Poor fueling may add power so check your AFR (I doubt this is the issue). Two reasons 1. too lean or rich your leaving power on the table and 2. a different controller may help if yours is setup to batch fire. Sequential injection better atomizes fuel improving combustion. Liquid fuel cannot burn but it reduces combustion temps.
Weak suspension leading to trenching (I would bet on this as 1 problem). My 600T 154x2.5 would drag the running boards and soak up HP. 154" tracks tend to trench... you can't go forward if the sled cannot get up on plane. It takes more effort to plane out on a smaller track (couplers helps this). Imagine a boat not on plane...it takes a lot of power to push through the water. But, once it pops out on plane, the boat speeds up. Adding a coupler can help with a collapsing rear under load. But, it makes the sled less playful.
Slow spool can result from too aggressive of helix, too much weight, or bad weight profile. You seem to pull the weight fine given your RPM, so I don't think it is a weight issue. I would try a weight profile that is less aggressive in the transition with the same full shift. If you dont know clutching ask someone who has done it (i would bet here too). Also, if the clutches and belt are getting hot on long pulls it is slipping, which soaks up power. The remedy is different clutching or reduce boost to eliminate slippage.
Those are some initial ideas. Try clutching and adjusting your suspension, but check clutch temps first. Careful, they can burn you if they are slipping. You should be able to touch them with your hand shortly after a short to medium pull up the hill. They will be hot, so be careful.