Generally the probability comes down to the size of the range. So for, say, a 4 character password, the password space the number of available characters raised to the power of the number of places in the password.
For example, a bank pin - 4 digits, 10 characters (0-9) - 1000 possible passwords, making the probability 1/10000.
Now your problem is harder, since your range is not all available passwords, you have removed some of the highly guessable passwords. What you're going to have to do is figure out how many potential passwords are eliminated by each rule, and make sure you account for rules overlapping... for example 12345678 is both a sequence AND all characters. Then take the total password space, subtract the passwords that are forbidden by each rule, making sure not to count a given type of password twice.
I'm not sure what you mean by "it cannot have the word "johnbook" " perhaps I'm being way too literal - obviously "johnbook" is just one password. Do you mean it can't have that particular word, or it can't have any known common name or short word combination? For example, is "bethdesk" also forbidden? What is the size of the dictionary being checked and all are all word combinations long and short forbidden? You should be able to use combinatorics to figure this out, but you need the algorithm or rules of password checking to know how much this limits the size of the password space.
Also, virtually any word combination is also going to be an "all character" sequence - so have you basically eliminated that, or is the system checking for obvious substitutions - like "passw0rd"?