Ad-hoc range

Line of sight certainly -- but walls and stuff limit the effective range. I suspect you'll be okay as my own environment is probably similar -- speed may not be the best.

Experiment with channels -- the different frequencies work better or worse depending on environment . Also choose a channel 5 stops from the most powerful neighbouring wifi.

can you share internet through it?

I rather doubt it, but have never tried. The original internet connection would presumably be via an ethernet connection to one of the machines ?

yes it is