I think you have a very good service motion. I really like it. I hope my daughter's will get there soon.
You already knew about the toss on the first serve. Another thing I noticed is the stance.....your back foot moving back and front instead of just front. Don't think it is wrong or inefficient. This could be how you find balance/compensate on your left knee injury. If that is the case, look at the video of Isner's and Tsonga's serve above. When you want to work on exploding to come around and making contact for your first serve, I think Isner's legs pushing will preserve your left knee more. Depending on the nature of your injury but just something to think about.