I have a bad back (scoliosis, pinches nerves) and a regularly inflamed hip thanks to rheumatism, but both issues got less on the keto-diet. Basically I couldn't properly excersize either, due to physical pain and extreme fatigue. Then I found out something that gave me hope: "You can't out-run a bad diet". Diet comes first, physical activity a distant second. So even with limited ability to actually do stuff, first the low carb/high fat and then the Keto diet helped me lose weight and get my bloodsugars down. Right now I'm able to walk -for me- long distances, like 5 miles or more, without collapsing in a bawling heap after a mile. The only reason my back still gives out every now and again is because I haul my camera's around, and that's a price I'm willing to pay: I can still have a few hours of my hobby before I have to look up a chair to support my spine.
Looking at your various issues, I do think going keto (20 grams of carbs or less) would get the most effect in the shortest time. If you're in this much pain, I think the sooner you drop the weight straining on your spine, the better. Otherwise I'd say take it easy with LCHF which is moderately low carb to low carb, rather than the extreme approach... But it might help you the fastest. Forget about calories for the moment, only pick those numbers up again *if* your weightloss stagnates. Do remember that if you reduce the amount of carb intake drastically you'll probably get carb-flu: fatigue, headaches, overall aches and pains. It's normal and lasts a few days, up to a week or two at most, while your body becomes fat adapted: burning fat rather than sugar to give you energy. It really does feel like a flu, but think of it as a detox. If you fluctuate from keto to moderately low carb it'll last longer because your body won't know which way is up. So pick an amount of carbs, and try to stick with it. Starting at 20 grams and under your body goes into ketosis: fatburning rather than glucoseburning... It speeds up things quite a bit far as weightloss goes, though if you prefer LCHF, it'll probably help you drop weight and bloodsugars too, just not as fast. And drinking electrolyte drinks like coconut milk will help with the flu-isch symptoms, as will bone broth. Anything salty too, as at first you'll lose a lot of water weight (yup, you'll be in the bathroom often), and you need to keep hydrated. I got a few dizzyspells which had me grabbing the kitchen's salt shaker, it always helped; but then I already have low bloodpressure.
Take care of yourself eh.
