Trainee needs advice

Unless you're in CA or TN, run your tandems back to about hole #11 counting from the very front and including the one taken up by the stop/stabilizer bar. Set your tandem there and try it.

I have found the trailer to be way too squirrelly when set to CA or less. That will also make for a smooth ride.

Regarding the water. Look at the stack. If there is liquid dripping out of the top, that's really bad news and will need repair ASAP. Open the reservoir cap and turn the motor on. It should not "blow bubbles" in the coolant. Have your mentor rev the idle up on it and look for white exhaust. Steam. Bad news again. Sniff around the under dash area. Your nose will tell you if there's a heater core leak. The truck shouldn't be using water/coolant. Crawl around that motor to see if there is a water leak. Look under it when you park and shut the motor down.

If he's blowing turbos and losing coolant, I'm inclined to lean toward a head/head gasket problem. This could create bigger problems with the DPF system (if equipped) if it is not taken care of quickly. Ask me how I know? I had a Cascadia with these problems.