As thoughtful as this letter is- it might not be possible for them to answer. Even if there had been no funny-business any legitimate company would hire a lawyer that would advise answering none of these questions. What if they were to answer you wrongly about one of these questions? Perhaps just from not 100% understanding the situation? You or someone else would turn around and go after them about that later.

It's a legitimate letter, but I think any lawyer would advise "no comment". It's just too risky to tell you the truth- innocent or not. Indeed, perhaps the things you point out in your letter about their "50BTC" limit, or "first come first serve" might be the result of them trying to come up with a clear, concise, and honest communication to the community, as quick as possible, the only result of which is more accusations and mistrust.