Hi -- I applied for a CRBA for my son late last year. On the DS-2029 form, I documented everywhere I lived in the US since birth (which was no easy task -- I moved 11 times before age 18). I documented all periods of time spent in the US (+ locations) after age 18. Sounds like you have passport stamps to back this up.
I also provided a copy of my university transcript, which they looked at. I also made available copies of old utility bills (from 2009-2010 -- I simply had old digital copies in my email somewhere), voting records, and tax returns -- but they did not review these. The DS-2029 form indicates there are a variety of documents that can be used:
"3.Evidence of the U.S. citizen parent(s)' physical presence or residence in the United States prior to the birth of the child. Such evidence may include but is not limited to affidavits, school, employment, tax, bank, and medical records, utility bills, rent receipts, or other official public documents. Evidence of time spent abroad working for the U.S. government, U.S. Armed Forces or qualifying international organization, or as a dependent child of a person working abroad for such entities prior to the birth of the child is also acceptable in some cases."
Even if you have been overseas for the past 8 years, a previous tax return could demonstrate physical presence if you worked for a US employer and had a W2.
Just some ideas -- good luck.
