Re: Jon Snow
I thought it was obvious why they did this now: Jon has just announced that he is going to Winterfell and drag the Watch irrevocably into the Game of Thrones. Pretty clear, really. They may not have agreed with his other decisions, but they did not go directly against the mandate of the Watch.
I thought just the same. Having all hair burned and alive means that she's most likely almost fireproof.
But back to Jon. For me its quite confusing that he was murdered at that moment, after wildlings are all over the wall. Basically he is only link between wildlings, the watch and queen men so I think that killing him will unleash swift mayhem as Tormund and wildlings are likely to take his side and strike the watch and queens man the moment Jon got stabbed. They outnumber watch, and in bloody, unorganized close combat should do better then watchers. Moment Jon got stabbed situation was very dangerous and even with Jon alive there was danger of violence breakthrought. It may be there waren't more dagger strikes after this 4 because carnage could begin just a moment later. If so watch can be utterly destroyed, or badly damaged (if they would fight their own civil war amongs their own ranks). Jon would be responsible of destruction of brotherhood that traced back thousands years, full of remorses and regrets, so that mayhem can suit sadistic approach that GRRM likes. Also he can become some kind of leader to the wildlings. Maybe new king-over-the-wall-at-this-side-of-wall. That would bring another pack of doubts to him.
I thought it was obvious why they did this now: Jon has just announced that he is going to Winterfell and drag the Watch irrevocably into the Game of Thrones. Pretty clear, really. They may not have agreed with his other decisions, but they did not go directly against the mandate of the Watch.