Varies slightly between agencies, but most/all quote you a salary after Korean taxes have been paid. The Korean tax element can count towards a tax credit in your country of residence, but that will be something that you will be responsible for.
Can't really help you with schedules as it's going to depend on which fleet you are applying for. But broadly speaking you get 9 days off in a row plus 2 days leave plus 2 days to travel. This should ensure that you get 11 days off at home. You can take up to 7 days leave at a time in addition to your 9 days off, but you would have to pay them back later.
You can live in Toronto if you choose, but if KAL do not fly there more than twice a week then you will only be positioned to, and from, the nearest airport on their network.