You may be rolling the fondant too thin. As far as wrinkles are concerned just make sure you have a smooth coat of BC underneath and ever so lightly tug at the bottom as you smooth with your hand. I haven't had a rip in my fondant yet. I think mainly because the thickness.
if I ended up with a crack this big, i would have started over again - not much you can really do other than that or cover up with more decorations.
If you have small cracks like on the edge of a cake you can take a bit of royal icing dag it on the cracked areas and then "rub" in with your finger or sponge and this can disperse the cracks - works mainly for cracks that have happened because of the fondant drying out too quickly.
To avoid cracking... you need to gently lay the fondanct on the cake and then "relax" it around the cake... gently pushing the fondant onto the sides of the cake and easing it into shape. If you try to tug it in any direction too roughly misshapen fondant and cracks appear... same goes for square cakes - this was what was advised to me and it works every time... just remember... "gently gently" and it'll all work out fine.
when you are smoothing out the folds that occur as your lay the fondant on the cake, make sure you smooth the top, then smooth (at this point just using your hand) from the top straight down (not side to side). You use one hand to lift the bottom slightly, while using the other hand to smooth it top to bottom. Then continue on along the cake.
It also helps if after you lay the fondant on you tim the bulk away (if you have any) before smoothing. Once you really get the hang of rolling out the correct size it won't be an issue, but for me, this was a crucial step at first. I cut away all about about the bottom inch. Then smooth. Then do the final trim.
And DEFINITELY make sure the cake is smooth before applying. Any ripples in the buttercreamor lumps ni the cake will be magnified by the fondant. I use fondant cakes as practice for getting smooth buttercream. I make it as smooth as though I were not using anything else, THEN I put on the fondant.
I've corrected this exact problem before. I took a razor knife and cut a square surrounding the mishap. Then I roll out another piece of fondant to fit the size of the cut out square. I glue it back to the cake with bc and smooth it out with my smoother. VERY GENTLY. You will still see the lines where the fondant is connecting but you can fill that with some RI (especially since it is white) and smooth either with a small spatula, paint brush, or popcicle stick. Make sure you don't overlap the fondant - you would rather have a hair space that you can fill in with the RI. On your particular cake I would remove the small flowers in the area first. The crack can still be seen - but much less than what you are seeing now - it will be acceptable if you do all of this very gently! Let us know what you decide to do and how it turns out!