“I've lived throughout my adult life outside the US. I have never earned any income in the US and as I was unaware of my obligation as a US citizen to file taxes annually, regardless of where I work or live - I have not filed taxes for any of the past years.”---->Even if you have never earned any income in the US, as a US person, I guess, you are subject to US taxes on your US source and world wide income (that you earn overseases). As long as you pay tax(es) on your world wide income to foreign taxing authorities, you can claim your FEIE on 2555/ foreign tax credit on From 1116 on your US returns, federal/state returns.
“ I have a questions regarding form 2555-EZ:I'm not sure how to answer Part II, line 10a or 10b, since I am filing for three years concurrently. So, I'm not sure how to answer if I've filed form 2555-EZ or not after 1981.”---->I guess on 10a form 2555EZ, you do not need to enter anything since you NEVER filed the form 2555EZ after 1981.But now you are trying to file Forms 2555EZ for 2009/2010/ and 2011. So, as you did not file Form 2555 /2555-EZ after 1981, you need to go to line 11a on 2555EZ.