I don't think there is a general answer. I have to quit coffee when I try to quit smoking (it reduces the craving and helps me to sleep at night), but I know people who have quit substituting the tobacco with huge amounts of coffee. You will have to find what works better for you. Good luck!

Very high. I only stop when I start getting the jitters. although, back when I smoked, I was never one that had to have a cigarette and coffee together, but I hear it's very common.