Where to find glass 'support' requirements?
You still have too many unknowns to make such a calculation, e.g.


Wind load needs to be taken into account.
Snow load needs to be taken into account.


The above loads will totally depend on whereabouts in the world you are installing said glass.

For total peace of mind (and most likely to cover yourself legally) you really should hire the services of a a qualified structural engineer to perform such calculations.

Rule of thumb, back of a cigarette packet calculations tend to only get people into trouble further down the road.