Mortgage rates went up because 10 and 30 yr bond yields have spiked. Also, during the yield collapse a few weeks ago, banks got flooded by refi requests and it exhausted banks’ supply of available dollars for mortgages.
Banks have an practically infinite supply of money. They just issue it when they create loans. What they lack is the capacity to process the loans, not the funding.
Your estimates? Is it true that Banks encashed $1T at 0% the Sunday before? Why did Mortgage rates go up?