Casting in a glass Bell Jar display

We were asked to embed small pieces in a clear polished resin dome. They are looking for a standard ‘bell jar’ display shape like a glass dome 6in diameter by 12in tall. A straight cylinder with a dome at the top. The kind of jar you would use over display item like a delicate swiss clock or a butterfly display.
I am wondering if we can just buy a glass piece and then use polyester resin directly into the glass so that the glass is both the mold and the final encasement. Then we wouldn’t have to create a mold and try and polish the piece we cast. It would just be ‘done’ and glass on the outside, suspended objects in the inside encapsulated in resin and hopefully clear as glass through and through (presuming we don’t get bubbles). I would cast upside down. Pour a partial layer in to about 4inches, then pre-wet the items being embedded, pour additional resin and place the objects. Then mix a final batch to fill the volume. So I have a couple of questions:

1. Will the exothermic reaction crack the glass (will the resin expand cracking the glass?)
2. Which resin should I use?
3. How much resin will I need?
4. If my embedments are at 4 inches from the inverted bottom of the dome will I see seams in the different layers of resin I need to pour in? What change in hardener would I be looking at adding (I saw your note about modifying the amount of hardner in larger castings and if you have a prior layer setting up when you pour the new layer down.

Your response is so greatly appreciated! I am a bit intimidated by this project.