Can you answer my questions about applying for a Canadian passport?

1. When I was born, I was given my mother's maiden name. Later, my parents got married, and I had my name legally changed to my father's last name when I was 16. My birth certificate originally said my mother's maiden name, but when I had my name changed, they sent me a new birth certificate with my father's last name on it. Is this going to cause any problems? Which last name do I put under "last name at birth" and "former last name"? Do I put the name on my birth certificate, or do I put what my last name actually was when I was born?

2. I worked at two places that went out of business. I am filling out the forms on the computer, and it yells at me for not putting down a proper phone number. How should I indicate that these businesses no longer have phone numbers because they no longer exist?