How many Tax Exemptions should I claim?

You CAN'T claim EXEMPT unless you have valid reason to believe your tax will be ZERO.

On your W-4, you claim withholding allowances. EVERY rule of thumb is WRONG.

The best most accurate way to determine how many allowances will come closest to withholding your actual tax liability is the withholding calculator on the IRS website.

Well, you'll claim 2 exemptions on your 1040 next April BUT the number of exemptions you should claim on your payroll form can be something completely different and we don't have enough information to give you a precise answer.

Since this will be the first year of Trump's new tax laws, it's a bit difficult to determine how your taxes are going to be affected. Looking at your information, you'll probably just take the standard deduction, and not bother itemizing, so you won't be declaring the mortgage interest paid in 2018.

So, I'd go with 0 for now so that you cover the taxes from your 2nd job.

Once you pay your taxes next April, you can readjust your withholding so that your 2019 tax bill will be as close to $0 as possible. (owing $0 is the ideal - not getting a rebate, which meant you were lending money to the government...for free.)

I'd claim zero since you have two jobs and are MFS.

Exemptions would be 2, but exemptions aren't claimed until you file your tax return after the end of the year.

What you claim on a W-4 are allowances, not exemptions. You probably want to ask how many allowances to claim.

Married separate is usually a very bad idea. I'd claim one.

MFS filing status sucks. Don't do it if you don't have to. If you have lived apart from your spouse before July 1, 2018 you may be able to claim HOH status. Claim 1 if MFS or 2 if HOH.

Use the withholding calculator at irs.gov.

Note, $4000 after taxes is meaningless. Your taxes are determined by adding up all of your jobs, not just the first one.

The IRS has a VERY simple calculator for this on their website