one other thing
please review this IRS document (the 2018 version has not been posted, but the concepts are similar) which explains how to split the deductions (table 1, page 5) and all the things you can't deduct / take credit for when filing as separate (page 6) . Their point is that most of the time, but certainly not always, your are better off filing joint.
https://www.irs.gov/pub/irs-pdf/p504.pdf
