Window for pressurized chamber made from laminated glass?
I would agree that you should be using laminated safety glass (ballistic glass) instead of solid glass. The reason glass is typically not recommended for pressure applications is that it tends to fail catastrophically without giving much notice that it is about to fail. Minor scratches tend to act as stress concentrators and crack initiation sites. lamination tends to minimize this problem, but unrelieved internal stresses are still a potential issue. That is why plastics such as acrylic or polycarbonate are preferred for such applications, they tend to cold flow instead of shatter, giving you time to sort problems out.
I don't know if it is commercially available yet, but a few years ago Raychem was working with the DoD and the University of Dayton on what was billed as "transparent aluminum" in a tip of the hat to Star Trek which was actually Aluminum Oxynitride (synthetic sapphire essentially) for use as bullet resistant window glazing. It was about twice the strength of conventional ballistic glazing.
I would suggest instead of using a rectangular opening, you should consider a round opening, or one with significantly rounded corners (not unlike aircraft windows) to prevent stress risers in the corners. DeHaviland learned that lesson the hard way with the Comet.
I would suggest talking to an application engineer from someone like PPG or Pilkington about this application and getting their feedback, the life you save might well be your own!