Does last-minute addendum to closing paperwork have any force?

[Gary Fritz]

My son just (yesterday) bought his first house. It turned out I had to co-sign with him. I was honest and told the loan underwriters that I was picking up a new Tesla this week. They said I couldn't get a new loan, as it would push us over the level of qualifying. Fine, I said, I'll write a damn check! They weren't even satisfied with that. They said they would cancel the loan if I bought the car before closing. Finally we got the message that buying the car with cash AFTER the loan funded was OK, as their requirements wouldn't have any force after that.

Then yesterday, at the closing table, I discovered they had slipped an extra letter into the closing documents: "To whom it may concern, I do not have any plans purchasing (sic) a Tesla. I have decided not to move forward with this. Please let me know if you have any questions. Thank you, (signed) Gary Fritz."

I said "I can't sign this, it's not true." They said if you don't sign, you don't close. The deal blows up, my son loses his house and his earnest money, the sellers lose their new house, probably other penalties. I also couldn't delay the closing (again) without breaking the deal. With a gun to my head, I had no choice but to sign.

I'm supposed to pick up my new car on Monday. If I do, I think I risk bank-fraud charges. So after anticipating it for years, I'm going to lose the car I ordered NINE MONTHS ago. If I order another one, it will cost me $9000 more at current prices. But given that overly-broad and vague letter, I'm not sure I can EVER buy a Tesla without them claiming fraud.

It's especially stupid because the car wouldn't put the loan at risk.  My son can handle his mortgage, but if he can't, I have more than enough cash/stock in my accounts to buy my Tesla AND buy his house outright! Plus over $1M in real estate equity that provides $3500/mo rental income (which pays my $3200/mo mortgage), plus a decent-but-declining income that will be supplemented by $2500/mo Social Security in a few months. I think their demand is unreasonable.

So: Does that letter have any validity? Is it enforceable, even signed under duress? Does it apply after loan funding? Am I gonna lose my car? :-(