You could ask for additional upfront deposits (double deposit, last months rent) if you're confident, but I wouldn't unless they were $100 or $200 off the 3 times rule.

Tell them you want your deposit back in full plus compensation for them breaking the lease and any extra costs you incurred (eg did you have a cancellation fee for movers-I doubt it as you said you didn't know when you planned to move in).

So, you definitely want to require a security deposit from them.Lastly, the $1250 in rent wired above is probably misleading.

However, I’d think most contracts have a deadline for performance where you can then terminate and get your earnest money deposit back and move on.

Take a higher deposit if you want to rent to them would be my recommendation

Lastly, it could be that the bank is going to portfolio your loan at below-market pricing because they want the entire banking relationship (deposits, transaction processing, consumer lending, etc) or simply want the risk (yield).Lots of local and regional banks have been retaining loans at really aggressive pricing recently as the current environment makes this favorable for them.

I'd immediately go to a higher deposit, several months paid up front, etc. 

Nothing herein is legal advice.Effective July 1, 2024, California Civil Code section 1950.5 generally prohibits a landlord from collecting more than one month’s rent as security deposit, whether the rental is furnished or not.

My realtor/PM says $0.95 to $1.05 per sq. ft. is a reasonable monthly rent for a 4 BR/2 BA property in that area, which (according to the BiggerPockets calculator estimate I did) is enough to cover the monthly payment plus the above costs I mentioned.I anticipate putting down my deposit and earnest money in the next few days. 

The seller could simply retain the deposit.