i walk around a lot without a walker you can just tell im walking with a severe limp.
6 weeks is still very early days in this year long recovery. You have a severe limp becuase you are not using your walker, and your knee is telling you that you need the support of it.
Ive started doing the treadmill on my off days of PT, i do a high incline
It is way too early to be doing a high incline. It was months before I could comfortably do any incline, let alone a high one.
It still seems to shake a lot when doing certain things.
This is telling you that you are doing way too much for your stage of healing.
Back off most of this PT and use your walker, or at the very least, a cane.
Give your knee a chance to heal. Go back to basics and rest, ice, and elevate, and this is what will improve your ROM. It is way too early to think about an MUA.
Regaining our ROM is more about Time than repetitions of a list of exercises.
Time to recover.
Time for pain and swelling to settle.
Time to heal.
Our range of motion is right there all
along just waiting for that to happen so it can show itself.
In the general run of things, it doesn't need to be fought for, worked hard for or worried about. It will happen. Normal activity is the key to success.