The issue is do you want to leave your current sponsor or not? You don’t specify this… In most cases if the contract draws to a close and both parties wish the situation to remain a new contract is entered into.
1a. Normally yes, the Labour contract will run concurrently with the Residency Visa which is of 3 year duration as well.
1b. No, you can transfer to a new employer without exiting. Bear in mind though that your contract has another 9 months to run, the Labour Law can change a lot in that time.
2a. Yes and no, under the current law you would be banned from working for 6 months (if you did not get a NOC), your family don’t’ work for your employer so are not banned…. But see the point bellow relating to residency sponsorship.
2b. Before your residency sponsorship is cancelled in September (by your employer) your family will have to be cancelled from your sponsorship (as you do this in your own right). When this happens you have 30 days to leave the country or transfer your Labour card to a new employer. After 30 days you would become illegal and would start accumulating a fine. If you can transfer your Labour Card within the 30 days you can then re-apply for residency for your family if you still meet the sponsorship criteria, note this (residency) is a new application and not a transfer as with the Labour Card.