Well.... three months later, (today) all that's been disproved.
To explain - The Eighth Doctor may have taken the De-Mat gun, but it wasn't the Eighth Doctor that actually MADE the Moment (the De-Mat "bomb" that obliterated Gallifrey and the Daleks). That was actually Hurt's "War Doctor" and the Time Lords.
And it was the trauma of surviving the Time War and the wounds inflicted from it that caused him to regenerate into Eccelson's "Ninth Doctor."
Sadly for you, though, absolutly none of what I've said is "theory" -- It's all confirmed fact by BBC themselves.
Watch "The Night of the Doctor" mini-episode that shows the Eight Doctor regenerate into Hurt's War Doctor, and how he
spicifically states that he is not part of the Time War and never was until that point. And BTW, the Ninth Doctor was born from the War Doctor's death at the end of the Time War.