Ay me, I do appreciate what you are enduring. I could not sit properly until after my epidural, that was about 4 months. My chiropractor had nothing more useful to suggest than to type standing up.

At least you do have one chair in which you can sit comfortably. What are the chances of getting a couple more chairs like it at garage sales or the like? Also, you might consider sewing a quick slip-cover for the chair back, incidentally covering up the "ladder" back. Out of sight, out of mind.