Hi ladymayin. Well you've been through a lot of frustration, I imagine. I had < 90 ROM for 4-5 months and felt pretty low about it.
When an ortho does a manipulation, they put you under and, I'm told, grab the leg just below the knee and gentle push the leg to bend, to break adhesions. It takes minutes or less. Ideally it's a fairly gentle effort and only pushed as necessary to break those adhesions. Those muscles have had a limited life all this time and so you will get the essence of muscle strain out of the deal, which can be treated with ice, elevation and NSAIDs, and narcotic pain med as needed.
It' tempting to then try to push the leg to bend but most people here have found that you have to go gently. There is an initial backlash (swelling, pain) after MUA and limited ROM (although the OS may have gotten a good number during the procedure). Eventually when things settle down you can slowly work on better ROM.
I'm curious about the PT efforts to get bend over the past year. It would provide some possibly important background to know. Interesting also that many orthos will not perform this procedure at this point. I'm guessing you have a pretty conservative ortho, which is a good thing.
If it weren't for pain and guarding, these could be done in the office (!!) My ortho said when he first practiced that's what they did.
So fear not. This is the best next step to make things better for you.