So you have the proof, but don't want to provide it, and you say you did this research for free, yet now want 3 BTC to prepare a report.
Hmm. How about this, just show the proof that the tax document is connected to the XC dev, and we won't need your report. You save time, I save BTC, and you stop the whole scam in it's tracks, thereby doing the community a service which you so righteously proclaim is your goal. Because here's how it goes otherwise:
1: We ask Dan, he say's "No, that's not me"
Has Dan already been asked and denied it explicitly(And I mean
explicitly as he likes to play games with his answers)?
If it is true, and he does owe a substantial amount in back taxes that is scary for anyone who lets him hold money. It doesn't automatically make him guilty of theft though. I doubt his plan is to run off with the money to be honest. I think if the tax issue is real then it sheds some light on what his motivations were for getting involved with someone like Prometheus and his group. I think he's in this for profit, pure and simple. It was possible that he was naive at the time, getting involved with Promethus, but his staunch defense of him after reading the chat screenshots, going as far to call him 'ethical' pretty much eliminates that one. Even with the most 'charitable' reading of Dan's words.
I wouldn't completely discount the potential of some sort of 'hack' or whatever where coins go missing though. I also would never be investing in a project lead by someone with these sorts legal issues if it's true. Too much pressure, government doesn't mess around. US Gov has seized BTC before. Not the IRS though as far as I know.
The odds of there being another Dan R Metcalf in Marshfield seem pretty slim considering it's not a big city really. Could be a cousin or something though if we really want to stretch it. My money would be on it being him though.