Aztec:
Bummer. Hot spots are technically the beginning of a blister. Friction irritates and wears away the delicate skin of non-calloused feet and causes a hot, burning sensation. Too much friction will form a blister.
If you really want hot spots, join the Army and go into Special Forces or join a Ranger Batallion. You will quickly find your feet are more important than any other part of your body when you are unable to walk due to blisters/stress fractures.
I've seen guys feet look like raw hamburger meet from humping heavy rucksacks while patrolling for days on end, with the dermal layer(s) completely removed on the achilles and ball. Sometimes worn away to the point of bleeding. Literally, skinned alive. Ouch!!!
I never got a blister in the field because I trained my feet properly. I had callouses over 1/4" thick on the balls of my feet which was enough to prevent blistering under the most extreme situations, although I did get some hot spots once in a while.
I don't know how some guys continued with their feet torn up they way they were. The pain must have been excruciating. I didn't want to find out what that felt like so I prepared for it.
So what's the great secret that will toughen your dad's feet??? Have him spend all of his time indoors walking barefoot, no socks. He can do it outdoors as well, but that can get kind of nasty, hygine wise. Simple and free. What more could you ask for???
He will quickly develop nice callouses and the hot spots should be a thing of the past.
Put his cleats back where they were before providing they were correct to begin with. If they are not set properly, you will create another problem while trying to fix the first one.
Good luck!!!