Stephen, this one's for you.
Marriage to a US citizen does not protect a LPR (lawful permanent resident) from losing his/her permanent residency if the LPR and their US citizen spouse decide to live outside of the U.S.
Typically when an LPR expects to be out of the US for longer than 6 months for a temporary stay abroad but has no intent to relinquish their US residence, the LPR can apply for a "re-entry permit." However, CIS takes the position that even with a valid re-entry permit, absences of 1 year or more constitute "abandonment" of permanent residency. However, residency may be abandoned even if less than one year where person lives and works abroad.
It's best to wait on that job offer abroad if you can until you can become a US citizen. Once the LPR becomes a US citizen (usually in as little as 4 years after LPR grant given current processing times), the former LPR can live outside of the US as long as s/he desires without having to worry about being allowed to re-enter.
One other issue I noticed in your posting, Stephen. If you become a LPR based on employment, if you immediately leave the company and go work abroad, you also bring into question whether you ever had a bona fide job offer since you "left" the company right after you got your green card. This could be very difficult to explain to a new officer at the airport when trying to re-enter the US.
