You're right - that happened to me too. I continued on the Lupron and finally my progestrone came down.
Here's the thing no one answered for me - if my progesterone was elevated as if I ovulated through the Lupron, why did the US taken at the same time as the blood draw show completely quiet ovaries with no evidence of ovulation? I posted that question on this board I believe several wrote that that didn't matter. It was the elevated progesterone that messes with the lining development. But still, why would progesterone become elevated if no ovulation took place?
That's not helpful really but that was my experience. (FYI - I have no known issues just DOR and shitty eggs, 4 failed OE IVFs, normal FSH last time it was checked, I just turned 43, boo hoo.)
What does SG plan to do for you? For me I was part of 2:1 shared and they waited for my progesterone to fall. But if that didn't happen within a certain period I think they would have cycled without me and I would have taken the frozens.
To your other questions, I always leaned toward a sET of a blast but I was forced into a 3 day transfer because of the holidays. I had a perfect 8 cell transferred, 1 8-cell, 1-6 cell and 1 5-cell to freeze. The fresh transfer was a BFN. And now I am in the 2ww for a day5 FET transfer of a poor quality blast and a morula. They never told me what happened with the last embryo. So for me I would definitely transfer two for FETs and a single embryo for fresh. But now that I have a failed cycle under my belt I may think differently next time.
Good luck. Don't let this freak yo out too much. Despite what they say, I think Lupron being ineffective is more common than is reported.