Was it suggested to start Cardiac Rehab? I too have had my valve replaced with a tissue valve, but my situation was very different. My condition was congenital and I was in very good shape going into the surgery and was running at 7 weeks post op.
However, my father had bypass surgery a few years ago and was in very poor shape. I got him into cardiac rehab following surgery, as it was a safe environment for him to begin to find healthy habits and find a routine that helped his cardiovascular health while being monitored.
The more active you are the fast you will heal. But sometimes that takes being in a safe environment and making sure you are not causing harm and someone is there to watch you and help keep you safe. Sounds like that would be a good option for you. It should be covered under your insurance and I know it def is under medicare (in the US).
As far as the numb chest, yes. The nerves were cut. I'm actually still numb along my scar. It took many months to begin getting the feeling back in the area. That's pretty common.
Also, my father did have some memory problems and personality changes following his bypass surgery. He did also have a heart attack though and a stroke the year before. But he doesn't really have many memories following the surgery or even rehab after.