I really didn't keep good records with my crypto. I'm thinking of just including money in a check specifying it's for crypto and hope that quiets them. It's not like we will get audited, we will just get a bill in the mail.
Not sure I follow. I'd avoid mentioning anything about Bitcoin/crypto on your tax returns, though. That's just asking to get your name put on an IRS shitlist.
When you say you didn't keep good records, why can't you get those records now? Can't you export your exchange trading records and deposit/withdrawal history? It's a bitch to go through, but it's probably possible to piece together the records.
Since you are experienced in stocks, you must know that every broker provides a P&L statement to their members which is a summary of all trades executed through them along with buying and selling price. It also mentions how much you have earned or how much you have lost in total. I believe the exchanges in US should be providing that for crypto trades as well.
Nope. Coinbase provides a P&L statement (although I've found inaccuracies with mine in the past). Most do not. Altcoin exchanges definitely don't, and like the OP said, that's significant because like-kind exchanges don't apply.