Re: lightwgt.climbing stick fully conected.
mamba, I think most all of the 20' sticks are made of steel and are going to be pretty heavy and a PITA to transport. There are a number of good sectional sticks available these days that are fairly light, easy to deploy, and easy to carry. I use the very cost-effective Hawk Helium 30" sticks that weigh about 3# each and they have double steps which fold in making them easier to transport. Four sticks (12#) should easily get you to 17' or so. There are even lighter but more expensive options.
You mentioned issues with the lineman's belt. You might want to try a small change in the way you are using it. Try keeping it positioned around the tree so that it's above your waistline. Then, try to get used to not leaning back so much, staying in closer to the tree so you alleviate the pressure on your back.
BTW, I too am retired, out of shape, AND have had back issues and this works good for me. And, like Keith, I also use a tree saddle when hunting public land. Its versatility is unbeatable. Good luck!