Flexion is 55 and extension is 15. I have lots of work to do!
Don't feel that you have to work hard to achieve good Range of Motion (ROM). It will come gradually, as time passes.
It's not exercising that gets you your ROM - it's time. Time to recover, time for swelling and pain to settle, and time to heal. Your ROM is there right from the start, just waiting for all that to happen, so it can show itself.
There's no deadline you have to meet, either. There's no need to rush to get ROM (Range of Motion) because it can continue to improve for a year, or even much longer, after a knee replacement. There isn't any deadline you have to meet:
Myth busting: the "window of opportunity" in TKR
While your pain levels are still so high, it's important to stay on a regular regime of medications. Any exercise you do has to take second place to that.
I really want to sleep in my side, too. When will that be possible again?
THe nufrses put me on my side for short periods while I was in hospital, for a change of position, but it really wasn't comfortable.
It's best to stay on your back for a while longer.
When you do try sleeping on your side, have your operated leg on top, with a pillow between your legs.