Yes if your 2021 is now lower you can get the 2,800 Recovery Rebate Credit! It is really based on 2021. They only used 2020 to send the checks out fast.
No do not subtract the #1 payment. That was only for 2020.
See IRS question 2 here,
2021 Recovery Rebate Credit — Topic C: Eligibility for claiming a Recovery Rebate Credit on a 2021 t...
