Welcome! Good for you for not just giving up on yourself. Sounds like you have your hands really full with being a single mom alone and then add in mobility problems. Wow girl! That's a lot!
I have also heard of the Sit N Be Fit program but haven't tried it myself. I would bet though that increasing range of motion in your upper body would have to increase your chances of losing some weight.
Jump in on some threads and get to know the rest of us. There is nobody here who is going to say "you can hardly walk, what do you expect" ... That is not the way a supportive forum should behave and we don't have that around here.