"Spouse left at beginning of 2017". I take that to mean you and your spouse are separated. You can not do anything with her without her permission.
The $4050 rule does not apply to spouses. But, that's academic. A spouse cannot be a dependent.
If you two can agree to do so, you may file as Married Filing Jointly and that means you can effectively claim her.
Otherwise, you may not claim her as a dependent.
Your only other choice for 2016, is to file as Married Filing separately. You may claim the kid either way, if he was born in 2016; regardless of who he currently lives with (you won't be able to claim him in 2017 without her permission, if he lives with her now)
