Petzl Climbing Gear has an ascender that would work very well for going up and down your tree if you have a climbing rope tied above your stand and at ground level. If you've ever seen it, it looks like a looped handle, which it is, with a place for the rope to go through. It grips the rope and only slides up the rope so you can hook it to your harness on the ground and reach out and slide it up every other step up the tree. You could even hold it in one hand all the way up, using it for support to climb.
Coming down you would hold your thumb on the lever that allows the rope to slide the other way, and slide it down a step or two at a time. If you fell you would hang from it until you could get hold of your steps and take your weight off it. Then you could continue up or down. Your rope would be tied tightly at the top and bottom of the tree with no slack and right against the tree, between your steps. A gri gri that Petzl also sells would work even better, as you then could slide it up the rope and after a fall, while hanging from the rope, you would only need to reach a handle which you pull out to descend at your desired speed. They also sell harness and rope and such for climbing and I have used many of their products. They ain't cheap but as someone already said your life is worth more. I weigh in at about 240 on a good day and would trust to climb to any hieght with their ropes and equipment. All this stuff is tested for ten thousand pounds of falling weight so I'm never coming close to breaking it, and a real climbing rope stretches a lot but doesn't break, which takes most of the shock out of falling.
Went and checked prices at REI and found the ascender costs $70. and the grigri which has the descending handle and is the best, is only $95. But of coarse you need an 11mm climbing rope too.