reminder: jumbo loan rate is higher than conventional loan

Frankly, 4000+ is too big, think about the maintenance cost. I don't think A is the right choice for u and your family. In terms of mortage, the general rule is not to carry a mortgage which is more than 3 times your household income.

B is 13 years old and you need to prepare some $$$ for roof/air conditioner/water heater/etc replacement unless the current owner already did it.

Just my two cents