Obviously we are all different but with the bike, my physio started me pedalling backwards as far as I could and then forwards as far as I could but not a full pedal rotation, next time I started like that and then it just happened that it went to a full pedal. Slowly and surely - am now up to 10 minutes on the bike with some resistance!
Also interestingly, the top of my scar was very similar to yours about the same time, I had TKR on 12 August and thought it was infected. I returned to my surgeon and it was the internal knot stitch that had not dissolved. He was able to remove and it healed very quickly. It will be interesting when you return to the Surgeon to see what he says.