racheldiane, this may or may not answer your questions, but it may give you some leads toward answers. Here is a link (I have not figured out how to post in-line photos here) to a DIY backsplash in a powder room re-do last year. The grout lines between the small glass tiles (Senio "Il' Vetri": http://www.getstile.com/glass.htm ) were 1/8" like your hex tile; the grout lines around the larger porcelain (Senio Trapunta Bruno: http://www.mosaictileco.com/senio_trapunta_ceramic_tile.htm ) tiles were a little wider than 1/4". The grout that we used was Laticrete SpectraLock. SpectraLock is an epoxy grout, and therefore never needs sealing. Never, ever. Here is a link that might be useful:

We used STT's SB solvent based sealer on the stone tile and the grout in our most recently renovated bathrooms. It is very easy to apply, and has extremely minimal odor. I also used it to seal the travertine floor tile and grout in our FR/guest bedroom/entryway. A big job made easier with our choice of sealer! It does a great job, too. The White Thassos lining the niches in our tub surrounds looks as good as it did the day it was installed.

Two things-- First, have him caulk first. Residue from the solvent based sealers that are usually recommended for this might keep the caulking from bonding to the tile later. Second, there's no big deal with sealing the grout. All you have to do is make sure you wipe it off before it dries on the tile.

I think I see the slight stain you are describing, but I don't understand the large white areas in the image. Folks over at the John Bridge Tile Forum may be able to help with some advice, if no one comes in here with any.