For SMPTE input - just use the 3.5mm jack on the Mac - it works fine.
I also use a PC Bal Box (Interspace Industries) to isolate the signal - or any other similar DI box.

For Audio Output - use 3.5mm for analogue.
Or use the digital optical output and a digital to Balanced Audio box - (Behringer SRC2496 Ultramatch Pro) - also isolated by optical connection.

MIDI - hundreds of boxes out there.
M-Audio and MOTO seem to work fine... lots of other too.

S