I am no expert, either, but I have experience in the +60 area...

First of all, I agree with Montanero's comments, especially working with your doctor - very important.

It is critical to become,and remain, active. Almost anything will do, and will be better than inactivity. Gardening and housekeeping are two mundane activities that are often recommended.

Aerobic activity is critical, and walking is easy to undertake. Hopefully, there is somewhere 'outside" that will work for you. A treadmill in a small man cave sounds rather difficult.

Search around and find routines that work for you.Consistency is critical...You need aerobics, strength (weights/pushups, etc) and flexibility/stretching working together for the best benefits.