From the log it seems, UFOAI is located in C:/Program Files (x86)/UFOAI-2.5, while Radiant is in C:/Program Files (x86)/UFORadiant-1.6.0, whereas imo it would need to be located in C:/Program Files (x86)/UFOAI-2.5/UFORadiant-1.6.0. Maybe it is even required to be C:/Program Files (x86)/UFOAI-2.5/radiant, but not sure about that.
You could try to create a folder named 'radiant' in C:/Program Files (x86)/UFOAI-2.5/ and copy/paste the content of C:/Program Files (x86)/UFORadiant-1.6.0 there. Afterwards, line five of the log should read "XMLRegistry: Importing XML file: C:/Program Files (x86)/UFOAI-2.5/radiant/user.xml"
I am not familiar witht that kind of stuff, but I think Radiant looks for the script files using a relative path (like ".../base/ufos"), not an absolute one. So it needs to be located exactly in the ufoai main dir.