Heres my advice. Its not pretty, nor a magic solution.. But it is accurate.
I take it you have filled out the security forms several times. And over the course of a couple days to a couple weeks, google got back to you and told you that they couldnt verify that you were the account owner.
Google does have a customer service contact number, but only if you are a paying google adwords, adsense user. Or a paid google apps organizational account.
Have you tried signing in with the old password ***** used to use? If that didnt work.
Theres only one way back into this account.
That old phone number with 75.. You need to find an old utility bill, or call a friend or family member who might remember or have that phone number saved.
Once you find out the number. Then you are going to need to contact the phone company who you had that number through. And you will need to reactivate the phone number.
That way, you can have google send you a text or call you with a verification code so you can reset the password ***** the account and re-open it.
There is no other way into the account.
If you have further questions or concerns, let me know.
Senior Technician and Network Switching Systems Operator / Maintainer.