Dinner at the CN Tower is expensive
Dim sum is awesome!
There are also some Korean BBQ ($10 for Lunch gets you unlimited beef, pork, chicken, fish, squid) places downtown.
Some All-You-Can-Eat Sushi ($17.99-$25) that you could try are AjiSai and Natural Sushi.
Other than Dim sum in Chinatown, you could try hot pot, I usually have it at home so I'm not sure what the prices are like.
There's also this website
http://www.toronto.com/events/ which gives you the dates and locations of some events going on in Toronto.