From what you have said, filing 'married filing separate' would be best (unless you would really like to see your spouse suffer!
![Smiley :)](https://www.talk.uk-yankee.com/Smileys/classic/smiley.gif)
).
It may seem questionable to someone under 30 concerning the Social Security contributions, but when you reach 66 (and the odds are you will) the additional years of contributions are very much appreciated.
For 2018, the IRS threshold for MFS is $5. The threshold for self employment remains at $400. The standard deduction for MFS is $12,000 if under 65. But yes, some CPA's say if income is under $12,000, you don't have to file. It's logical, but I question the accuracy of the statement.
Since all your employment and income arose in the US, and you were resident in the US prior to and on 31 Dec. 2018, other than filing MFS, the normally filed forms for someone in the US in that position should be all that's needed.