1) No, you don't have to fill-up this form individually for your father. It's need to be filled-up by you and the co-signer (if your wife is co-signer) and your mother (there need signature from principal applicant).
2) You are right, you don't need to fill that up separately for your father as your father's information is already there as a spouse to your mother.
3) You need Marriage Certificate of your parents, Marriage Certificate of your's if your wife is a co-signer, your birth certificate,
your parent's birth certificate (both), your parent's passports photocopy, your parent's photos, application fee receipt. If you provide Nikkahnama English translation you have to also provide a certified copy of the original Nikkahnama and an affidavit from the person who completed the translation. Check the
Document Checklist [IMM 5771] so that you don't miss anything.