Well fuse 1 goes to your ignition switch so that would most likely be where your problem is.
From that fuse it goes through your fire wall and splits into 4 wires (all of these are yellow) and these four goto your ignition switch.
Just as a guess I would say there is a short in your switch, afterall it is part mechanical and can wear out and cause shorts.
If it was me I would grab a switch from another vehicle and see if it starts then. The switch in your truck is the same in hundreds of ford vehicles. You can take a look at the switch here and click on compatibility to see all the ones that the switch is in:
Just about any ranger from 95-04 has the same switch.
The switch is located right underneath the steering column.