Say for instance you have a chain that has a safe working load of 200 lbs. If I wanted to hang an item from 4 corners, each with its own chain would I be able to hang 800 lbs? Or is there some other variable to factor?
The chain configuration does not just affect the amount of support. It also controls the angle of the seat of the swing as it moves through its arc.
If you use a single hook on each end, the seat is always perpendicular to a line that extends from the center of the seat to the hook.
If you use two hooks on each end, the seat will track differently, depending on the length of the chain and the relative positioning of the hooks. One example is a parallel configuration.
Some configurations simply will not work well (e.g. if the space between the hooks is much wider than the space between the attachment points on the swing). Also, chains of different length will cause the seat angle to change (tip forward or backward).
As several comments point out, it is essential that whatever attachment system you use, the chains and the ceiling supports must be strong enough to hold the swing, the people and then the load must be multiplied by at least two or more to account for ther moving load.
You need to just install a new loop. But, fortunately, the fix is pretty cheap and simple. I don't think glue is going to do it.
You'll want to shop around for one that matches the color, size, and so forth, but here's a ring on Home Depot's website as an example, and another one from Menard's website. You might want to take the chandelier apart first and take the broken ring with you test the color/fit at a store if you can.
First off, cut the power to the light.
Then, at the top of the chain, there's likely to be a metal plate (usually with a similar ring) and/or thumbscrews that hold it to the ceiling box. Unscrew the ring or thumbscrew and lower the plate from the ceiling, exposing the wires. Untwist the wire nuts and take the light fixture down.
Here's a better step-by-step than I can come up with: How to replace a light fixture.
Carefully un-thread the wires back down the chain to the broken loop and disassemble the chain/loop connection. Remove the broken loop from the top of the chandelier.
Install the new loop, feed the wires through the center hole, open up the last link of the chain and bend it back together around the loop (This is a great time to make adjustments to the length of the chain if you want to) then feed the wires back up the chain, through the metal plate, and re-attach the wires and re-install the top plate, etc.
Best of luck!