I can't help with any of it, except to say that whether or not Edward Wheeler had an E in his birth reg is irrelevant to him appearing as Collard in the registration.
If he was born illegitimate he would be registered under his mother's surname of Wheeler. But he could have chosen the name Collard - or any other surname - if he wanted to, without any legal niceties. You can call yourself any name you want as long as you don't intend to defraud and of course in those days there was less fuss about identity and fewer people had either bank accounts or passports or driving licences.
I wouldn't assume Norma is dead if you haven't found a death for her. My parents married in 1953 and my mother is still very much alive!
I suppose you could try the phone book for Norma Wheelers in Portsmouth, or place a letter in the Portsmouth newspaper with the largest circulation, appealing for information.
You also can't assume that Paul Wheeler who married Norma is your chap either. Wheeler is a relatively common surname. Unless you get the marriage cert and it states his father was John F Collard (which it might not) you can't be certain about it.