Sounds as though you have found the right place to look.....you will
need to dig a little further into the circuit though..... try to follow the
wiring diagram to find the source that is drawing the power that keeps your
engine running..... the fuse is there to protect the circuit, but something
in that circuit keeps drawing amperage.... try to find what else is wired to
that circuit....a wiring schematic would help or you might be able to look
at one from the dealer if you ask them...

good luck..

Fwed

As far as the running with IG switch off goes, the most likely cause is
a bad ignition switch.  That problem can most easily be caused by B+
remaining available at the coil and ignitor, which is supplied through
the 'run' and 'start' contacts of the ignition switch.  A really bad
carbon track or smashed/broken contacts could conceivably pass enough
current to keep that little ignition system pumping, along with the
idle fuel solenoid open in the carburetor.  It could also explain your
rapid battery depletion.

Regarding the blown fuses, here's an idea: follow the large white wire
that attaches to the B+ stud on the alternator.  It should disappear
into a thick harnass near the engine.  Follow that harnass all the way
to the fuse box with the "engine" fuse that keeps blowing.  Somewhere
along the engine, possibly near the exaust manifold or a moving pulley,
you may see it make contact with metal.  Look for wear on the harnass
jacket and insulation at that point.  Alternately, firmly wiggle the
wires with the engine running to see if you can blow the fuse, then try
to determine where the short is.

Toyota MDT in MO