Hi! What disability? You can pm me if you're uncomfortable sharing here
But if you're currently on the heavy side which make high-impact cardio difficult, the best indication of fat loss is an elevated heart rate while exercising. This means that anything that keeps it up will be good to start with such as the exercise bike or even something like yoga (which i highly recommend even to my bodybuilder clients)
As for the diet, I am really not a fan of diets like keto and atkins since I believe in a balanced diet. The most important thing is finding the diet AND food you're comfortable with and allows you to build consistency.
Start off with basic portion control and finding the aspects of your current diet which you can reduce (not cut-off completely for now) that are bad for you.
I.e. decrease sodas from 2 cans a day to 1 then eventually none
So many people fail because they can't stick to their diet. Also research a ton on healthy recipes like chicken, eggs, etc and find the ones that you love
This'll let you prepare for when you start dieting seriously