Where the Soviet missile subs were at the time is unknown, but if a war broke out they would be sailing towards the US to make their attack. Some if not all would get through. After all the four subs the Soviets sent to Cuba eluded The entire US Atlantic fleet for weeks, and one of them was never detected. After receiving 50 ICBM's do you really think the US would be capable of defending itself against the (estimated 155+) Soviet bombers?
Yes. NORAD was its own command. With the Canadians as well.
All this assuming the 50 1st Gen Soviet ICBMs actually worked, and hit what they aimed at, but I doubt they would have targeted NORAD or TAC. They would have sent them after SAC bases and cities, keeping some in reserve. I'd bet at least 75% of them would be targeted for SAC Bomber and Missile bases as well as CNC.
Heres a chronology
http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB75/subchron.htm of submarine activity during the crisis. You see we had a far better handle on it then you seem to think. The thing about their missile boats is they use to hide them under the ice, or on the edge of polar ice, and there wait for deployment orders. That gives them very predictable approach lanes to the eastern seaboard and as you see we had deployed a huge ASW contingent to look for them. Once we decided to look for these Soviet subs we found them in short order.
Yes a few would get thru. Yes the war would have been catastrophic for us, "at least by how we define such things", nobody is arguing that. But the entire Soviet Union would have been a radioactive smoking ruin. America had a large preponderance of nuclear forces and thats why the Reds backed down. Can you really argue against that? 20% of SAC's bomber force was in the air at any one time during the crisis, the rest were dispersed all over the place and could be in the air within 15 mins. Khrushchev himself later told his son, "Kennedy had us by the b---s but didnt squeeze".
Even the rabid Red ideologues didnt want this war. In their theory communism was going to eventually win out against its enemy anyways so's its best if theres a world left over for it to inherit. I suspect the big Bosses in Russia also didnt want to lose their dacha's, mistresses, fancy cars, or the pampered futures for their children. We arent all that different after all.
The result of this entire mess was a big build up of Soviet nuclear deterrence, the concept of MAD, Euro Realpolitik, and eventually detente. Of course eventually the end of The Cold War came about cause the Soviet economic model could not sustain an arms build up against NATO and the west. So the missile crisis had very large implications across the board. Who knows what would have happened if the nuclear forces were only equal, or close to equal? We might be living in a "Boy and his dog" type of world.
I served in SAC during the height of The Cold War. None of this stuff was a joke and i can only imagine what it was like being on DEFCON 2 for days on end. All it could take was one accident or Loon making a mistake. If I remember right the Soviet Commander in Cuba was authorized to release nuclear weapons so all it would have taken was for him to have a bad day.