Hi!
I don''t know that much about soudfonts, but for my little experience, it seems you''ll never find the perfect (free) soundfont. What I do sometimes is render the midi files track by track with diferent soundfonts each time (I choose the best for each track) and then I mix all the tracks.

Here are some links you should try if you haven''t:
http://www.personalcopy.net/home.htm <- they have Kamac Dist. guitar, the best guitar SF Ì''ve try.
http://www.powermage.com/fluid/ <-- Great SF
http://www.hammersound.net/ <-- Tons of SF''s

For converting midi to mod, I don''t know if Awave (http://www.fmjsoft.com/)can do that, but if it doesn''t I doubt that any other program can.

Hope it helps!
see ya