The VT180 Technical Manual
helped a lot (EK-VT18X-TM_001 VT180 Technical Man Feb83.pdf).
Most of the timings are present. Chapter 6 covers the inner details of the DC011 and DC012 in painstaking accuracy.
That said, the present, character oriented
code works reasonably well (at least the Rainbow 100 path, which could be generalized).
Different termination characters on VT terminals shouldn't pose a problem