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On the label of the Crossbow Herbicide it will tell you how long after application you can safely begin planting. In using any pesticide, the most important thing is to read the label carefully. This article will tell you more about herbicides: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/how-long-does-weed-killer-last-in-the-soil.htm
I could not find anything in the literature about Crossbow's effect on worms.

Yes, I would definitely recommend that you do something to encourage drainage to prevent waterlogging your plants. A berm is another idea for diverting water. Depending on its locale, you could also choose to implement a rain garden. These articles will help: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/yard-drainage-problems.htm, https://www.gardeningknowhow.com/special/spaces/creating-and-using-berms-in-the-landscape.htm, https://www.gardeningknowhow.com/special/spaces/building-a-berm-how-do-i-make-a-berm.htm, https://www.gardeningknowhow.com/special/spaces/rain-garden-design.htm

This article will help: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/nitrogen-plant-fertilizer.htm

Unless there's coolant in it, the wiper fluid itself shouldn't pose too much of a threat. However, I would suggest hosing the garden down real good to dilute everything. This should help.

Your soil is alkaline, or very sweet. Ideally, for most plants, you want a pH of 5-7. This article should help with lowering the alkalinity: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/raise-acid-level-soil.htm

It should be alright to simply lay down some landscape fabric, black plastic or moist newspaper with mulch on top to control the weeds.