I have a herniated disc between my C5 and C6 vertebrae, so upper backache is a thing. I had physiotherapy, and luckily I got a guy who was experienced with musicians and explained some of how the weight of an instrument is distributed. Based on his suggestions, I raised my bass up from just above waist height to mid-belly height and it's made a big difference. In terms of the biomechanics, it's now sitting in a spot where the muscles in the middle of your back are compensating your balance instead of the muscles higher up your back and in your shoulders. Also, the lower you have your bass, the more work your shoulders and upper back have to do because of the position of your arms. You have to raise your elbows a little to keep your wrists straight, but not a lot, and it becomes second nature after a while. Conversely, if you have lower back pain, wear the bass lower as it moves the distribution of the weight upwards, which sounds counter-intuitive, but it works. There's a "sweet spot" there that you'll find.
Setlists - bigger font and use more sheets of paper?
Screen on pedalboard - if you're a Zoom guy, consider an upgrade to the B6. The screen is bigger, brighter and, most importantly, in colour - there's different colours for the different blocks, which makes differentiating them without having to necessarily read them much easier. Love my B6. Just wish it was a full steel chassis and had a built-in expression pedal. It has all the same stuff in it as your one, so recreating your patches will be easy.