I'm not saying there's nothing more to it and I'm not saying you're a crazy nutjob. The nutjobs are the ones who decided what they want to believe first and then discard the facts that don't support them while embracing and twisting around any remaining facts into a nice warm, cozy conspiracy theory.
The only issue I have with what you wrote above is this notion about "The Government" as if it's this one single 600 pound Gorilla that sits on a throne that makes all these decisions alone. The government is a collection of bureaucratic organiztions, each one with its own agenda, its own political leanings, and its own never-ending thirst for more power and funding.
When I hear "my government" did this or my government did that, I think of that in terms of policies and decisions that actually made their way through that vast bureaucracy and finally emerged into the light of day as public policy that is implemented. So attacking Afghanistan and removing Saddam Hussein from power is something my government did. Putting out new contracts for MREs is something my government did.
Did my government ever think about attacking its own citizens? Some parts did, sure. As you pointed out, Operation Northwoods shows exactly that:
http://en.wikipedia.org/wiki/Operation_Northwoods
But don't miss the last part of that web page:
It has been reported that John F. Kennedy personally rejected the Northwoods proposal, but no official record of this exists. The proposal was sent for approval to the Secretary of Defense Robert McNamara, but was not implemented. President Kennedy removed General Lyman Lemnitzer as Chairman of the Joint Chiefs of Staff shortly afterward, although he became Supreme Allied Commander of NATO in January 1963.
So yes, some part of the government thought about it and some other part rejected (or didn't implement it). This goes on all the time with military planning. Do you really think we *don't* have plans for a First Strike on China/Russia? Just plans...do this first, then that, then that. I'm sure they're sitting in a notebook on a shelf in some bunker somewhere. Our government came up with those plans. But do they really plan on using them?
So yes, at point you're probably thinking "Now who's the nutjob? He's comparing attacking his own citizens with attacking a foreign country." True...that's an extreme example. I'm just saying the government plans for a lot of stuff...some of it makes sense and some of it is despicable. But the point is that they're just plans/contingencies/fantasies from some particular agency until they're actually implemented by "the government".
So yes, I completely believe some parts of the government are "planning" things like that. I just keep hoping that those plans never come to pass.
Did any part of our government have any connection to 911? Did some CIA funding make its way to some guy who knew something or did something or went somewhere that was somehow connected? Probably. And it's probably even money whether this happened on accident or on purpose...or even both. But was there a secret CIA "Operation Tower Drop" where they planned out how to make this attack happen? That part I doubt.