So the questions I have are:
1. Why did Cash App not accept the large BTC transfer, I have used Cas App over a year and have almost 100 BTC transfers equaling the amount that was owed and sent to me.?
I don't know if you are still on this forum or not, but just incase you are still here, or you come back in the future, I will like to tell you that your case is a case of scam, if you story is true, then it's rather unfortunate that you've been scammed, it is my advice that you should contact cash app support, maybe they can be of help to explain things more clearly to you.
2. Do you have to "warm up" a new wallet with some transaction history before it would accept something that might be considered out of the normal transaction amounts for the wallet to that date?
There is nothing like warming up a wallet before sending any amount of money into the the wallet, even if the money you are putting in the wallet is in billions or trillions of dollars.
If the person you are talking about has the private key or seed phrase to your trust wallet, then be rest assured he's out there to scam you even the more, my advice is that should not put any fund into that wallet anymore.