Sperm are present on the tip of the penis long before ejaculation. You definitely can become pregnant without the man ever ejaculating inside you. It only takes one resilient, microscopic sperm to find and fertilize the egg. Just what are the odds of that one sperm surviving and finding the egg are impossible to say. If it does make it that far, the odds are 100%. But no one can tell you "What are the chances."

Those things you cite are just not factual.

There are many reliable sites on the Internet such as the Mayo Clinic and the American Pregnancy Association which have information about your question.

You have another problem, besides the fertility of pre-cum.  A guy can begin the actual ejaculation process before he feels his orgasm.  Its different for every guy, and its different between lovemaking sessions for the same guy.  What he squirts out may not be very much, and it probably won't be very strong, but it can still happen.  And if it does, it does contain semen.

Sex without protection is a bad lottery game, unless you are both ready to be parents.  Sex the day after ovulation is a really bad game.  Don't play it until you're ready to have a family, in all fairness to you and the child.