You have royally screwed yourself with all that churning of non-Gmail accounts.

Yes, use a Gmail account. Yes, you will need to use a forwarding phone number that has not been previously used to claim a Google Voice phone number. There are no workarounds for this; it's an anti-fraud/abuse measure.
If you did already successfully set up a Google Voice account using a non-gmail domain, then you might be able to transfer its phone number to a gmail based account; I know this works between one gmail account and another, but I haven't tested it to transfer a number from a non-gmail account. Here are the instructions:
https://support.google.com/voice/answer/3527591?hl=en&ref_topic=1708124Here are my step-by-step instructions for setting up Google Voice on your OBi:
http://www.obitalk.com/forum/index.php?topic=8560.msg56460#msg56460