You are really just guessing at what the intelligence community has found about Flynn. More than likely, it is barely substantiated information, as has seemed to be the case lately with them. Anything more is conjecture on your part.
Its a ridiculous notion that someone who has dealt with the russians in any capacity is a security risk. Puts 100,000's of people in the USA in the same league. Even as bloomberg said, that's actually a non-issue.
Its the lying that is the issue, whether you believe it or not. There is a certain amount of lying that is acceptable (its the way it is, I disagree with it) in politics. Stupid things like the phone call are not acceptable to anyone.
Resignation is almost always better than firing from an optics perspective. Don't be ridiculous. Did Hillary fire her pet aid? No. She stepped down. You arguing about the "how" is pointless. The why is much more important, do you really think Flynn just "resigned" of his own doing? How pedantic you are, playing with the semantics.
End of the day, my point is the Trump org made the situation much worse then it had to be. It was stupid. Why you are so intent on winning internet points in something we basically agree on is beyond me.