The reason the treadmill works for me is because I look forward to it and there is zero prep time to talk myself out of it. Those were the 2 things I had to overcome in order to exercise/move on a regular basis. So a stroll around town would be great, but what would make you look forward to it (mentally) and miss it (mentally and physically) when you don't do it? Also, I don't let myself go over 30 minutes. NO MATTER WHAT. so there is no "oh I didn't do it yesterday so now I have to do an hour" BS, nope that was yesterday this is today, 30 minutes. there is no "oh I am on it now so I may as well do an hour" BS, nope that will change it from something I look forward to sot something I have to make time for!
Personally, I honestly think that once your body starts to heal, and your stress is reduced to manageable, and you get quality sleep, you will just do it. No "having' to do it, you will just do it. A healthy body wants to be in motion. If I were you I would force myself NOT to do any movement, until at least you are getting decent sleep. (Except for working out in the yard, or just being in the sun in general, I don't think that sleep is improved by exercise, I think it is the other way around)