This is the first time I was able to read on this subject and not be utterly confused. I am sure that if Queen Elizabeth was a direct descendant of King David, she would have made it known. There would be no reason to hide it. But like you said, we will never know with 100% accuracy.
As I’ve mentioned before, I just finished studying Samual and Kings and I’m in the midst of Chronicles. As soon as you pointed out the verses in Kings, the conditional promise, it rang a bell with me. I know many believe that in this scripture it is also relating to the coming of our Lord of Lord and King of Kings, Jesus Christ. I didn’t get that connection when I read those verses - God was specifically referring to the Kings of Israel…and like you stated, man failed the condition God gave.
So again, thank you for clarifying and presenting the facts the way you did. Many blessings to you!