Make a better tool !?
I made a tool which I used easily. It was constructed from a "rat tail" file similar to a chain saw sharpening file. I used a file because it is made of strong material. I bent an inch (or so) of the tapered handle into approx. a 90 degree turn. The handle portion of the file is not so hardned as the file proper, but IS strong enough that even if a little too small in diameter will still not break or bend easily. Also being less than 1/8 inch at the tip helps to find the pully hole and makes insertion easier.
There were 2 holes spaced at 180 degrees from each other --- are you sure you turned at least 90 degrees while looking for the hole with your tool?
2. alternate way. (If you are going to replace the belt for sure). Cut the belt off and then use a rubber strap wrench (from Sears or other source) to hold during removal. Once you get the pulley off you should be able to fashion a suitable tool (to use on installing) since you can see the hole and trial fit the tool for bends, shape and length.
Incidentally, I could not find a 93 300E with a 2.8 motor on my cd files....Would that be a 103 or a 104 type motor ?