1. Follow these general instructions on amending your 2019 tax return: https://ttlc.intuit.com/community/tax-topics/help/how-do-i-amend-a-2019-return-in-turbotax/00/123845... The result will be no IRA contribution. If the recharacterized contribution was originally filed as a nondeductible traditional IRA contribution, You'll need to manually prepare a corrected Form 8606 to explicitly show $0 as your nondeductible traditional IRA contribution; TurboTax will not automatically print a Form 8606 that has nothing but $0 on line 1. If the recharacterized contribution was originally deductible, you'll need to similarly prepare Schedule 1 explicitly showing $0 on line 19 and reflected on line 10, Other taxes. With no taxable gains, no other changes will be present.
2. No. Your explanation statement with the amendment will take the place of the 2020 Form 1099-R that you will receive near the end of January 2021 and you'll be able to ignore this 2020 Form 1099-R when you receive it.
3. The distribution amount needs to be the $6,000 adjusted for the loss. Assuming that the money is still in the Roth IRA, the Roth IRA custodian should calculate the loss and the distribution amount. If you actually did move the money to a traditional IRA by recharacterization, you'll need to do the calculation yourself and provide substantial explanation to the traditional IRA custodian to allow the traditional IRA custodian to correctly report the return of contribution on the 2020 Form 1099-R.
4. What you propose is permissible and appropriate.
