Hey Dr. Bob...I took your umbilic torus equations and brought the surface into a graphics program just for fun. Here it is as a transparent solid with an index of refraction computed.
I just bought a copy of Boothby's Introduction to Differentiable Manifolds, which seems to be comprehensive and elementary. I'm a bit excited about getting into it. Also picked up Simmonds's Brief on Tensor Analysis.
Hope you're enjoying the summer in Italy, maybe a nice gelati...