Sampling MIDI Via Parallel Port
Yeah, so i managed to find the answer all by myself, thank you very much. It had to do with very specific electrical details of the parallel port itself, which i now figured how to compensate for. The solution was both simple and elegant, and now all is working beautifully. However, since no one cared to address my specific question, instead preferring to focus on irrelevant details which i had already explained at length (but apparently no one bothered to read), i won't go to the trouble of posting the details here.

I guess the real take-home lesson is that dealing with this whole site is a massive waste of time.