Absolutely do not use a tampon. That's the worst thing you can do. The Diflucan is actually a pregnancy category C which means risk can't be ruled out. But one dose isn't expected to have any harmful effects.
I use 1/3 cup white vinegar in 1 litre of water, wash the area, it works wonders for me.
Yeah it's fine. Only one tablet and should work within 24/48 hours. You could always use live yogurt and a tampon that is safe as well