Received invoice payment for $3K that shows BOTH as a deposit and (incorrectly) as a PAYMENT deduction on the bank account. How may I fix this?

This means both sides of the transaction, debit and credit, use the same account.  To fix it, edit the transaction and change the account in the detail area to something other than your bank account.

Still, if you have created an invoice in QuickBooks, then when you get a payment for it, it should be recorded as an A/R Payment on account, and if so, then it'll never have this issue.  Once recorded, then deposit the payment using a deposit transaction.

I changed the description from the bank account name to Accounts Receivable and that eliminated the duplicate entry in the bank register.

There is still a duplicate entry in the Accounts Receivable general ledger account in the Balance Sheet for a -$3k balance.  I unmatched the duplicate transaction and deleted it.  Unable to match the bank transaction to the first Accounts Receivable transaction.  How may I fix this?

I changed the description from the bank account name to Accounts Receivable and that eliminated the duplicate entry in the bank register.

There is still a duplicate entry in the Accounts Receivable general ledger account in the Balance Sheet for a -$3k balance.  I unmatched the duplicate transaction and deleted it.  Unable to match the bank transaction to the first Accounts Receivable transaction.  How may I fix this?

I don't know. By "match" do you may apply the deposit transaction to the invoice?

When applying a payment to an Invoice, it is better create a Payment transaction and then deposit it. Don't create a deposit and try to send it to A/R. That's an uphill battle that QB Online makes it quite hard to deal with. QB Desktop is easier, but it's still better to record a Payment transaction for payments received from customers.