That tongue weight is worrisome. It would be easier to buy a different, larger trailer than add a third axle. Or, sell the truck and buy a dualie that can handle that much weight on the rear tires.

The huge storage box is the problem - you might be better with a 20-24 ft enclosed and have shelter too. That size trailer can be found no problem and great prices.

Sell what you have on eBay for $2200-2800 and take that money towards a better trailer. End up with something with better resale than a modded up triple axle is that thing factory? kind rig...