Your form needs a little work. I can see some anterior weight bearing going on there; you're coming up on your toes and breaking at the knees first. You need to break at the hips first. Hips back, hips back, hips back! Just focus on getting them back and the knees will follow as you descend. Practice with very light weight first, especially since you have no rack.
Also, going deeper does not trash your knees more. That is fucking hogwash. I have yet to see conclusive studies that suggest parallel compared to below parallel is harder on the knees. Somewhere around the 50-70 degree range is where you should stop if they hurt your knees. Once you get below about 70 degrees patellofemoral joint stress doesn't increase significantly, and you are getting to about parallel already.
By the way, good to see you squatting!