What OpenAL dll are you using? You could try the latest OpenAL Soft if you are not already using it. Download the openal-soft-*-bin.zip on the page and rename the openal-soft-*-bin\bin\Win32\soft_oal.dll to OpenAL32.dll and drop in it your ioquake3 directory.
ioquake3 only uses digital audio (no midi). Soundfont would not affect it.
Also, the SDL backend currently does not support surround sound.