The only way you'll find out is to tough out the PT and see if it works. If you don't try it, you'll never know if it will work. If the pain is decreasing, that means the rest that the pain has forced on you is easing the injury, and if you're icing, any inflammation may be going down. Time can do a job on pain, but if there's a structural problem neither rest nor PT will change that but it might take the pressure off enough to make it not hurt you anymore.
I can tell you with 100% accuracy that shoulder surgery is the worst surgery you can get. However, it does work.
I’ve had frozen shoulder in both my shoulders so I can empathize with you. The first one that froze, I was referred for PT and painful as it was, I did stick it out since I’d already had it for more than 6 months. My pcp did give me a steroid (cortisone) shot which made it much easier to deal with.
By the time the second shoulder started freezing the first one was well on the way to thawing and because I’d had the PT with the first one, I knew what exercises to do with the second one. After several months, my pcp did give me a steroid shot in the second one also, which, again, helped considerably.
A frozen shoulder can take 18 -24 months to freeze and thaw. It took both of mine approximately 18 months to get back to “normal” - that was with a steroid shot in each one, along with PT.
It’s tough to deal with the PT because of the pain, but it’s really quite necessary. My PT did quite a bit of massage, which was awesome. They also told me to alternate heat and cold. Cold reduces inflammation and heat helps with healing.
Personally, I’d go back to PT and stick it out this time, but also check with your doctor about a steroid shot.