One tip I would HIGHLY recommend, and the outlay is minimal. . .oh around $95-120. . . is to get yourself one of those tiny 5000 btu window units. You might also find a used one for a song. They weigh like 35lb. It will do a small living area, around 15'x15'.
Just put it in the attic or basement for a main AC system emergency. Having the family able to keep one room cool in 100F days till repair man can come is a major agony saver.
Plus dad isn't so much the a-hole for not replacing the AC system years ago.
