I thank you for the efforts you have made in trying to solve this installation issue, but after four or five attempts to install CC 2015 to no avail, it seems that, for whatever reason, the CC 2015 / Data Bridge upgrade is not working for me.
This means I will just have to forget about CC 2015/Data Bridge and keep working with what I've already got until I find a solution elsewhere. After all, there's basically no difference between CS6 and CC 2015 and, if there's any, it's hardly noticeable.
Data Bridge has apparently installed well in CS6, but if there are any problems any time soon I will have to return Data Bridge and request a reimbursement (what's WA's policy on that?)
It seems that, at least in this case, Adobe is succeeding in keeping CC 2015 customers from using Web Assist products.
Thank you for your attention.