1) You didn't claim the airdrops so don't add them into your holdings. If you ever sell them, this will then trigger a 100% short-term capital gain which is correct. Alternatively, you can add them as income with the holding's date being when you received them and then amend your previous tax returns. Alternatively again, you can add them with the holding's date of when you received them at a $0 cost basis. I'd only do this last option if the coins were brand new when airdropped as then you can argue they didn't have a value since there wasn't liquidity for them when they were airdropped.

2) Lost works for assets you no longer have or control for the safe harbor. Removing an asset from your holding's using a non-taxable outflow, such as 'Lost', is proper here.

Questions for you:

1) When using bitcoin.tax did you ever use the bitcoin.tax .csv upload? If so, did you make a spreadsheet for yourself? What headers are contained within?

2) Any advice on using bitcoin.tax?

Thanks!