Hi
1. If your PR card is still valid, yes.
2. You can stay until the PR card expires.
3. Your wife's PR status isn't affected by yours.
4. Yes.
You should note that if the OP doesn't meet his residency obligations, he will be reported at the POE. He will be allowed forward with a certificate of departure for 30 days in the future. He will either have to submit an Appeal to the Immigration Appeal Board or leave Canada. The IO when report the OP is supposed to canvass any H.& C. grounds as to why the PR should not be reported. The expiry date of the PR card means nothing, as a person could "land" 01/01/03 and their card would be valid to 01/01/08, but they left Canada the same date and didn't return for over 3 years, their card would still be valid, but they would not longer have PR Status.
The OP should read:
http://www.cic.gc.ca/english/resources/manuals/enf/enf23e.pdfPMM