I remember starting to ride again about 20 years ago after a long layoff. I was about 40 and also overweight. I started with 5 mi. I kept increasing mileage and was ready for Freewheel in OK after a few months. I suspect that you can ride easy most every day of the week and then increase your mileage once a week. I think you will find that your normal mileage gets easy and the only hard rides are those where you increase mileage. I think a 5 mi per week increase ought to be a reasonable increase for you.
I was also riding a mountain bike at the time.
If you can get your mileage up your weight loss should accelerate.