How do I get my ex off the title?

Changing title and changing the mortgage are separate issues. Do not assume removing someone from title removes responsibility for the loan; coordinate title changes with the divorce agreement, lender and legal guidance.
Separate the property decision from the loan obligation
Ownership, mortgage responsibility, equity, and the divorce agreement are related but different. A deed controls title; the loan documents control who owes the lender; the divorce process determines how the spouses must handle the property between themselves. Removing a name from one document does not automatically change the others, so the sale, refinance, or buyout plan must address each part.
Changing the deed does not change the loan
The lender is not bound by a private agreement between spouses. A borrower generally remains responsible until the loan is paid off, refinanced, or formally assumed with lender approval. Likewise, being removed from the mortgage does not by itself transfer ownership. Confirm both title and loan changes in the closing plan.

