Two things I noticed this afternoon:

1.) There is significantly more water in the truck's oil than before I changed the gaskets, and

2.) in the three times I've driven the truck since I put it back together, the oil pressure gauge has registered steadily increasing pressure.

This tells me three things:

1.) Obviously, removing the head, cleaning it, and replacing all the gaskets did not fix the problem,

2.) I made the problem worse by messing with it, and

3.) I completely wasted an entire week.

Not sure what the solution is at this point.