See here for good article explaining what income counts and what doesn’t for MAGI -http://www.healthreformbeyondthebasics.org/key-facts-income-definitions-for-marketplace-and-medicaid-coverage/
You pay all of FICA. Approx 15%
Is this paid when you file your taxes or this withheld and paid by the employer.
You pay, iiuc its treated like 1099
Correct. Not withheld.
So the rabbit pays the employers and employees portion? Like self employment tax? Does the employer report it on the 941 and w3 w2 as social security wages?