There is a difference between cum and pre-cum. It's quantity. There is more cum so there is more risk. There are risks in oral sex but not all risks are the same, and it is safer than fucking without a condom by far.
As far as taking it in your mouth and then spitting it out, I would rather just swallow it. If there are cuts in your mouth, I think it's better to just let it shoot down your throat rather than keeping it in your mouth for a few moments till you can spit. That is, of course, if your throat is not beaten to a bloody pulp by some guy with a monster dick.
And keep your eyes closed!