Question about non resident spouse and son

You can file Married Filing Separately or Married Filing Jointly whether your spouse lives with you or not.  To file Head of Household you must have dependents that live with you for over 50% of year and you pay over 50% of their expenses.  So if your son lived with you less than six months of the year (or otherwise supported himself) you can't take the deduction for him.  He should file his own return if eligible.  If he's not required to file a return I think you could still list him and just not take the deduction.

No.  You do not need to add your dependent if you are not claiming him as a dependent on your return.  It is actually better to not enter someone who you cannot claim on your return.  You can go to the personal info page and delete him. 

You do need to keep your spouses name on there, but you do not need to have your child name.  

Also, since you are married, you do have the option as Married Filing Jointly instead of Married Filing Separately.  By doing so, your spouse is choosing to be treated as a US Resident for tax purposes. If your spouse chooses to be treated as an US resident for tax purposes, and you want to file as Married Filing Joint, you can apply for an ITIN when you file your return.  You would need to include their income FROM ALL SOURCES WORLDWIDE (not just what they earned in the US) on your return as well and they would be taxed on it. If you choose filing jointly, you will need to print and mail your return along with the W-7 which is an application for an ITIN and any other required documents to the address in the instructions

@NewtoCA