I have to admit that I find this thread interesting, although I don't have much to offer by way of help.
I do find one thing a bit confusing though: it looks like the printer is serial. Yet you say you've got it working on a parallel port. I find that contrary to my personal experience with how this stuff works.
I've never used a printer like your model. Usually they use serial because they are intended to be too far away from the computer for parallel to work. I think parallel has a roughly 2-3 meter (6-9 feet - ish) limitation. The ones I've seen use a 25 pin serial cable - and it's tempting to think they are actually parallel, except that the male versus female tends to be backwards.
Also, I have to wonder about
TSP700. Sight unseen I would have thought that the "S" meant "Serial". Which would lead me to think that
TUP700 would be "USB".
So now I find myself wondering if somehow your problem has to do with serial versus parallel. Perhaps the port you're using is in fact serial and you don't know it? Perhaps the code you are using needs a different configuration to communicate with the correct port?
Greetings.
Albert