If you are filing, you have to declare your entire income, regardless where from - that you made in the tax year. It might be low enough to qualify for no filing but you are filing, where it was made doesn't matter in terms of having to report it but it does matter from perspective of paying tax on it.
https://www.irs.gov/individuals/international-taxpayers/foreign-earned-income-exclusion
https://www.irs.gov/forms-pubs/about-publication-519
These two pages should be of your and your husband's interest. You have to file since you do have GC, therefore substantial presence test does not apply.
The question is still in N-400, you will just simply respond to it "No" (as you have never not filed a tax return - provided it is true going forward as well).