What are my chances of getting pregnant with birth control pills, spermicide and withdrawal combined?

Pretty low. Obviously no plan is foolproof, but what matter most in this case are the pills. As long as you take it "perfectly" ie not missing any pills and being cautious if you take any medications that may interact with them, the chance of getting pregnant on birth control pills alone are good, the other methods add icing to the cake. If you are looking for an even more foolproof method, consider an iud.
Very little. Using all those forms of contraception correctly would make it seem almost impossible to become pregnant.