It's a bit late since your leaving in the morning, but have to give my 2 cents worth.
Your ball mount is at the bottom of the adjustment with the trailer still at a rising angle. That's why you don't have a lot of tension on the spring bars.
When you get back, flip your ball mount arm so that you can lower the ball mount until the trailer (empty) sits level on the hitch.
Then, when you have the trailer loaded, you should be able to bring the trailer and truck back to level and have tension on the spring bars.