I finally got the Pro version of Rack 2 and I’m on Ableton 9.7.7 and the vst plugin does seem to work so far. (Haven’t tested thoroughly yet.) But I noticed that the saved projects with WASAPI device preselected do crash Ableton.
If the device is [No device], then no crash and I can select DAW as audio driver. 
(Windows 10, Lexicon Alpha, Ableton 9.7.7, Rack 2 Pro 2.0.4)
A similar program is discussed in this thread.