As a permanent resident of the US, you are treated as the same as U.S citizens for tax purposes. I am attaching the following link to show the comparison between filing jointly and separately to help you decide :
https://turbotax.intuit.com/tax-tools/tax-tips/IRS-Tax-Return/Should-You-and-Your-Spouse-File-Taxes-...
-Filing jointly and having your spouse being overseas should not have an impact on your citizenship interview. For more information, check https://www.uscis.gov/, ( At the right upper corner, click on Need Help ? Ask Emma, is recommended)
