Just download this program instead, is more modern and lets you change MIDI in real-time:
https://coolsoft.altervista.org/en/virtualmidisynth
For the soundfonts use this link
https://archive.org/download/soundfonts_201910:
I highly recommend the ChoriumRevA.sf2 and if you feel nostalgic and wanna listen to the game just as you would have done back in 1999 with an Soundblaster AWE 32/64 download the AWEROMGM.sf2
A lot of nice sf2 out there, but i vote for those 2 as the best from that list.