Most of what you said there is pretty accurate.
FICA payments aren't deducted/deductible, it's just a separate tax on the same income.
If you are legally married, you have to either file Married Filing Joint or Married Filing Separate. If you go MFS there are a few shitty restrictions. If you itemize, he has to. If you have student loan interest you can't deduct it. There are other limitations, but those are the two I always remember.
Itemized Deductions - You have the idea down, but you can also add any state income taxes paid, any real estate or personal property taxes paid, or any large sales taxes paid if they exceed state income taxes. You can also add any charitable contributions here, and a few other things.
File as fast as you can if your ex is the type that might try to screw you over. If you are the one that paid the mortgage and you have the right to deduct it, don't let him claim it first, or don't let him file first with the standard deduction as it might preclude you from taking itemized deductions.