If the foreign country has a tax treaty with the US you will not have to pay US income taxes, see a consultant on that to get details. If you are in a tax free country you are exempted the first $85,700 then pay tax on the balance.
The immigration officer who interviews you for citizenship determines if you meet the physical presence requirements, I know a woman who lived many years in Florida on a green card, took a job at American Airlines as a flight attendant and was turned down on her citizenship interview because he believed she was out the country most the time even though she only flew domestic. Miami seems to be the worst for denying applicants. I was resident in New Orleans, showed my logbooks and they accepted that, I still had to satisfy the physical presence criteria, investigate that on your own, don't believe an unknown immigration lawyers statement.
Been there, done that.
Hope this helps
NG