Baron - I was in DVSM many years ago, drifted away once life got to busy.
Our local martial arts association did a pretty extensive comparison of the various systems out there and ended up recommending Zoom for two way communication up to about 20 or so. It's easy to use, reliable, doesn't seem to glitch, and they did a series of updates last weekend to fix the security issues. I've been on Zoom with 35 to 50 Folks and I don't recommend it for large groups - everybody's the size of a postage stamp and there's a cacophony of voices even with good speaking discipline. I wouldn't do more than 16. Sessions can be recorded locally.
For large groups you have to sacrifice two-way for bandwidth. We do 45 min Face book Live sessions every Tuesday, Thursday, and Saturday to about 100 students. They automatically record and post for later viewing. You should have a private page for your group to use Live.