More success! The issue I am facing now is transmitting, but I have a theory as to why that's buggered.
My Pentium Pro is a bit stuffed on cards, and other devices are definitely interfering with the modem, namely the mouse. It's a serial mouse, and when it's connecting I can hear it crackling to the mouse movements in the speaker.
1200 baud worked a lot better, which is strange considering I attempted that earlier to no good success, but I think it was my Obi's settings. Receiving is DEFINITELY reliable, which shows that there is definite merit to this idea. It may not be the best idea, but it's certainly not bad. I was able to get weather, and some other stuff over the BBS before the link crashed after my system sent a load of garbage characters down the line (:/)
I think now it's a matter of getting a more reliable box to do this. I love my Pentium Pro, but it's a bit of a pig in some places. I would LOVE to use my 486, as it's a machine that would have been more likely to see a proper BBS, but I need to do a lot of work to get it in a position where it can use the modem correctly. I namely need to backup my PC-DOS installation and install Windows 95, which will just take some time.
300 baud didn't work for the BTTF BBS. It only received garbage data, and I think it's just an incompatibility with the BBS. 1200 baud worked perfectly fine, however, with, as I said, the only issue being occasional bouts of garbage data being sent because of interference from other devices. All the IRQs are fine, the modem is on IRQ4, that isn't used by anything else, it's just my own setup, I'll figure it out.
Thanks for all the help, I will try to do a video to document my success, and I hope with another machine I can get this into a working state.