Correct Comma Use

Hello all,
I would like clarification on correct comma usage, so here are a few example sentences:

"Tom, who loved eating burgers, walked to Burger King."

"Mary saw Carl, a tall young man, who wore a green and red t-shirt."

"If Mark is wearing blue, then it's surely because he likes blue."

Also, if correcting any mistakes please explain why/support (with grammar rule/logic), so that I may better understand. Thanks.