I have three ruptured disks in my lower back and one in my shoulder blade area.
I have no problem reloading, sitting down, for maybe 30-60 minutes. I can rest, walk around, stretch, and get back to it after a few minutes--but I generally don't push it like that. I have Dillon 1050 presses and the long handle and smooth functioning are the main reasons I can still reload.
For a bench, I found a really rigid table with a thick top. You can find them at thrift stores. If it is in the house, you can cover the press and still have a fairly attractive table/desk in the "reloading" room.
I would say get a press with a lot of mechanical advantage (which the Hornady does have) and use lube for all your cases so the sizing step is eased. You may find hand-priming is easier on your than doing it on the press.
Talk to your doctor about what you can and can't do. My doctors's responses were almost always "If it starts to hurt, stop" and "Don't life anything heavier than 10 lbs." For me, ANY lifting or walking is a killer. I can't even help my wife with groceries, unless I want to take a couple Vicodin and lay back for several hours to a day.
One thing that has really been a blessing is the adjustable beds we bought a couple of decades ago. It very nice to find the position where your head is raised and your feet are raised the you remove most of the strain on your back. Also, DO NOT EVER have a back message unless there is someone to help you very carefully move onto your stomach. All the time your back is getting massaged, you are putting a load on your lower back. I did this once and when I got up, I ruptured one more disk and really damaged the other two. Any massage should be with you sitting up and leaning forward.
Unless there is surgery, you will probably just have to live with some pain if your try to do too much.