Second question first - I think that the thicknes of glass you need wont be able to be cut at home, they will have to be ordered to size.

First question - quite thick, maybe 2' or more. There was a thing on TV showing an 80kg man breaking through a 1' thick laminated glass window when travelling at 7 mph, you dont want to fall over and break your floor, or jump and break it, so thicker than 1'

You really need to contact a specialist. Most glass merchants only supply window glass, and probably don't have anyone who is qualified to deal with glass for structural purposes.
Laminated glass has several layers with plastic film between them. If there are two layers, you might do it with a glass cutter, if there are three or more, you need special equipment.

you cant use a glass cutter on glass tiles. you need an angle grinder with a glass cutting disc. i think a ceramic disc will do the job. have you had a structural survey done on your house? glass is heavy! also its very safe as flooring or walling, but not for windows. fire hazzard, no escape. i once threw a wrecking bar at 12 mill laminated glass and it bounced back!