I can give you a pretty close number. 22% for Federal and then depending on the state you live in perhaps 5% for state taxes (if you have state income tax.
First, the amount you tax out will be added to the other income in the return, so it would be added to the $70K or so already being reported on the return.
You say "we" so assuming married filing a joint return.
So if you don't take out say more than $10K or $15K, the tax rate should stay in 12%, and the early withdrawal penalty will be 10% so a total of 22% for Federal and then depending on the state you live in perhaps 5% for state taxes (if you have state income tax).
The reason for the penalty is that even with medical you can only exclude the penalty for the amounts that exceed 7.5% of your AGI (so $70,000 plus $15,000 taken out, is $85,000 times 7.5% is: $6,375 that would not be excluded from the penalty in my example).
If you do overpay you would get this back when you file the 2018 return.
2018 income tax brackets.
2018 Income Tax Brackets
Tax Rate Married Filing Jointly--This is taxable income (which would be in very simple calculation your income less the $24,000 standard education in 2018)
10% Up to $19,050
12% $19,051 to $77,400
22% $77,401 to $165,000
