You have to list the passport information of every single passport you had during the 5 years eligibility, so both, unless the old one is very old...
Also, only the bio page is required for online applications, but the whole passport for paper ones.
It can be. It's just a simple "please finalize my app in x days, else I'll seek mandamus relief", regardless of how it is sent to IRCC (webform, mail, snail mail to the IRCC office...)
No need to withdraw I think. Send a webform, say that you mistakenly put all the information about the father as unknown instead of everything except the name.