To fix the crack, go buy the cheapest torch you can find at Home Depot, then take a plastic bottle and melt it so that the molten plastic drips over the crack, the inside of the bumper of course, you have to take off the bumper to do that. It maybe a good idea to tape the crack of the outside (the good looking side) so that the molten plastic doesn't get to the good side but it may burn through the tape, so before doing that try melting the bottle and allow the plastic to drip on the tape you are going to use, if its not hot enough to burn through use the tape on the bumper. When the plastic goes into the solid state, one side of the bumper (the inside) is pretty ugly but the other side is smooth cause of the tape. Now you just have to paint the plastic the same color as the bumper. BTW if the tape melts use something that will not melt, you get the idea.
What do you think about that? Think it might work? Don't just go and do it, think it over, I would hate making someone do something that may ruin their car. It may just work perfectly but maybe a disaster, I never tried it. Oh, if the bottle doesn't melt the way you need it too, use something with a lower melting point, I guess you can try wax from a candle, but that will probably fall off fast.