How do I enter distribution of $20,000 (for a married couple) from my IRA to fund a portion of home buying costs? TurboTax only recognizes the single ($10k) distribution.

Only the first $10,000 from your IRA is exempt from the early distribution penalty.  If your spouse has an IRA they can withdraw up to $10,000 without penalty for the first time home purchase.

Each IRA only has one owner, there are no joint IRA accounts, and the rules apply individually to each owner.  Sorry, you owe the penalty on the other $10,000, and it's too late to make a correction to your accounts.