Can I connect a 100 amp sub-panel to a 200 amp main through a standard breaker?
Can you add a 100 amp breaker to your main panel?
  Yes you have 12 slots the double pole breaker will only take 2 slots.


Will you have enough ampacity to run everything with the new sub panel?


There is not enough information to answer fully but probably.

What are your other loads for the home?

Do you have gas or electric appliances / heat?
If your major appliances are gas (water heater, oven &amp; furnace) I would expect there to be more than enough to run a 100 amp sub, if your appliances are all electric you may have enough but the size of the home would also be needed to calculate your current demand.