What part of Virginia are you located in?
Your approach is completely off base. Spousal support is deductible to you, taxable to her as unearned income. You canot withold ANYTHING from it, she's supposed to manage the money herself. As much as you hate the idea, she's now got to figure out how to do this HERSELF. If you start out paying her that much, YOU are setting the status quo and she's likely to be awarded this amount.
How long have you been married? How many children and their ages? Child support is NOT deductible to you nor is it taxable to her. They are SEPARATE issues.
Are you planning to pay the mortgage for her forever? That's what you're setting yourself up to do. What length of time are you willing to pay these bills for her? Is she never to learn to support herself?
Spousal support is NOT a given in Virginia. Are you planning lifetime spousal support? Are you planning to do her taxes for her for the rest of her life? At what point does she become responsible for herself? There's a huge income disparity here, granted -- but better to assist her in getting an education if she needs one so she can be self sufficient.
Your taxable income would DROP to $5500 per month, her taxable income would rise to $3500 per month. If part of that is child support, that needs to be taken off the top. If she is on the deed to the house, she then gets half the deductions for the house -- by the time you do all that math, she isn't going to end up OWING anything and in fact, if there are children that are still able to be deducted on her taxes, she will be well within the income bracket to claim the earned income credit for the child, increasing her refund.
You haven't really gone into this in depth with an attorney, have you......there are so many more things to take into account here that you haven't considered.