Firstly, the science regarding the nebula was edited by my beta (loneranger1/Aragon101), who is sort of my science expert, and he said this thing would work. My theory is, though, that you would need massive amounts of power to detonate that particular
nebula (see how I save myself there?
), and only the strongest nuke Atlantis/Daedalus had would be able to detonate it. Ordinary weapons fire, or even the explosion of Wraith darts and 302s would not be enough on its own. Anyhow, it probably didn't come across very well, but in my mind they weren't fighting at the heart of the nebula, meaning the concentration of hydrogen was lower. But the nuke was detonated at the highest concentrated pocket of hydrogen in the nebula (thanks to the Asgard beaming tech), thus making a chain reaction that would really set the explosion off.
As for the Sam/John aspect, this will be explored much more in the future chapters. They haven't been together that long when SCoaFF starts, but in my world they had been forming a very solid friendship since Sam arrived at Atlantis in season 4, and that counts for a lot. I know all about the frat regs and Sam's clingyness to soldier mode, which is why things happened as they did in concern with hers and John's relationship (see chap 5). I had originally planned flashback episodes to explain how they got to the point where they actually decided to break the regs, but I haven't gotten to that yet.
What I do want to comment on, though, is that it seems like most fans thinks something awfully big and traumatic must happen in order for a character to break years-long habits of clinging to rules.
I don't mean that as criticism, but it makes me wonder if Sam is REALLY that much of a control freak, that she needs something HUGE to crack her out of her shell? She lost her father, but there's still only minimal clues in canon that she got together with O'Neill.
So I ask, what happened to an ordinary, long-time influence that is profound enough to make you want to risk losing everything you've held dear? I may be a romantic, but I'm also a realist.
HUGE impacts make for great Hollywood plots, but in real life, it's also the slow process over the years that changes you. That's what I want to point out in relation to Sam. Everything that's happened in SG-1 and SGA has led her to the point where she is in Some Corner of a Foreign Field. I hope people will believe it...when I finally get around to finish the story.
Hope that answers some of it.