Try this (just a hunch and as a test)
Once you selected the default synth in the Options area (before changing anything inside SynthFont) close out of that window AND PT.

Re-open PT, then try to make the rest of the changes.

If it crashes before you can successfully configure it, try moving the dll file to where John has his dll, then in PT, remove the synth from the list, close out, open again and relocate the synth in the new location .. maybe certain default files get saved to a given location and that is causing the issue (could be anything from permissions to compiled locations).

Make your sound your own!
.. I do not work here, but the benefits are still awesome