Here's what I do - it simulates the high direct heat and then lower, indirect to finish ( like on the real grill with multiple zones):
Put the 'grill' on the top rack (make sure its not coated or non-stick, that it can take high heat). (I do mean to put a pan under this to catch grease.)
Turn the oven to broil for a few minutes.
Prep your chicken.
Put it in the oven under the broiler for a few minutes (I can't really give you a time here because it depends on thickness and other things), but you're trying to promote that browning and a bit of char like the grill.*
After its been in a few minutes and browned/charred somewhat, pull it out and quickly flip it and repeat.
If your dish isn't fully cooked to your liking, move the item to the middle rack and turn the heat down some.
Pull it out when finished and Rest the meat.
Enjoy
To be honest though, for indoor grilling - I usually preheat the oven to 400, get some grill marks on a cast iron grill pan, and then finish in the oven. Its only when the volume is too much that I do the above method. Cast iron grill pan for a couple of servings has always been much less troublesome than the broiler which can bring items from tasty to ruined in record time for me.
*Some people close the oven door here, some don't - its the difference between if you just want to sear it or really start to cook it. I pretty nearly always close the door, but I'm also the guy who always puts the lid back on the grill.
Sometimes. Basically, this is the same as asking if glass is oven safe:
Generally, glass is oven-safe if taken from room temperature and put in a moderate-temperature, preheated oven. The key thing is to avoid temperature shocks (which will cause the glass to shatter). Some glass is specifically designed for oven use (either by being tempered or made of borosilicate glass). Often glassware will say if it is safe for oven use or not, and under what conditions—check the packaging or instructions it came with.
You also need to take precautions when removing glass from the oven. Do not set it on something that'll conduct heat away rapidly, such as a wet countertop.
Before heating glassware, inspect it for damage. Scratches, chips, etc. make failure much more likely. This applies to the microwave as well.
Note that non-glass parts of microwave-safe glassware may not be oven safe. For example, if it has a plastic lid, that should generally not be used in the oven (even though its OK in the microwave).
edit:
In response to your update, that oven is what would often be called a toaster or countertop oven. Those change temperature much more rapidly than a larger oven (which can be electric as well). So, generally, you'd avoid glass in them.
But, your glass says it can be used over a flame, from the freezer. So it's clearly one of the very shock-resistant ones, possibly borosilicate. I wouldn't expect it to be a problem. Just make sure to preheat the oven.
Also, since you know who made it, you can of course contact the manufacturer to confirm.
Best Answer
You can't use just any sheet of thick glass for your oven door. Glass for your oven has to be tempered to resist high temperatures. Untempered glass will likely crack pretty quickly with regular use. Moreover, an oven door usually made of glass which breaks into "rough pebbles" rather than sharp shards if it breaks, to decrease the risk of injuries if the glass does crack. If you replace it with a regular thick glass pane you run the risk of (worst case scenario) very sharp, very hot shards of glass exploding all over your kitchen one day.
Like @M.K. stated in the comments, your best bet is to contact the company and ask about replacements, or a reputable company that repairs appliances. They can easily secure an appropriate piece of tempered glass to replace the broken one.