1) Well the tax rate varies with the amount you make but basically:
Up to 9000 CAD/year exempt
Up to 23000 CAD/year around 20%
Up to 50000 CAD/year around 33%
Over 50000 CAD/year around 42%

But keep in mind that you have a lot option to lower your TAXABLE amount. ( School, Medical, GST and etc.) If you decide to move to Canada get a good Accountant. He can save you more than you can imagine

2) Cost of Living does depend. Keep in mind that ALL HEALTH and EDUCATION (up to University and except for some private schools) IS FREE.
You can rent a 2 bedroom place around 1200 CAD/month up
Grocery can be around 500 - 750 CAD/ month for a family of 3 - 4

Basically you should be able to live with a family of 3 -4 with a average monthly budget of 2000 CAD.

If you need more infor , especially about Toronto, you can PM me.

Cheers