how much is withheld on paychecks does not matter.
What matters is what is on Line 22 of Form 1040. That is your tax liability. Prior to the EV Tax credit, that line must be at least $7500 for you to qualify for the entire credit.
Be reminded also there is an income limitation. If you purcahse a new EV in 2023, your income must be below the limit - you can use your 2022 income or your 2023 income to satisfy the requirement.
Filing Separate is never a good idea for financial reasons. I have yet to see a case where filing Separate results in lower tax across the two returns than simply Filing Joint.
