What is this white fungus on my squash leaves?
This is powdery mildew. It is common with squash. This article will help:
https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm
A fungicidal spray that will wipe this out and is earth friendly is called Green Cure. I use it on my pumpkins, cucumbers and roses, it wipes out the powdery mildew and allows them to thrive.
I manipulated some of my squash plant's leaves so they wouldn't cover a couple of my pepper plants. Some of the stems broke.
It depends on where you broke them and how completely they were broke. If the break happened further down the plant and there are plenty of leaves behind the break, then the plant will like grow branches and be fine. If the stem was bent rather than severed, straighten it out as best you can and it may recover. To help it further, bury the damaged part of the stem under some soil.
If the main stem was severed and there are few leaves behind where it was broken, then you may need to replace the plant.
I have squash plants that are blooming but there are not any squash behind the blooms. I wanted to know if I was supposed to be seeing the squash behind the bloom or will the blooms fall off and the squash begin to grow then?
Squash plants always produce male flowers first, female (with the fruit behind) will come in later. This article will help:
https://www.gardeningknowhow.com/edible/vegetables/squash/squash-blossoms-falling-off-vine.htm
How much sunlight and water would the squash plant need?
Squash plants require plenty of light (full sun) and water (at least an inch weekly) throughout their growing season—watering with a soaker hose provides the best results, as this allows it to penetrate roots more easily rather than turning into runoff. This article should help you as well: https://www.gardeningknowhow.com/edible/vegetables/squash/how-to-grow-summer-squash.htm
They are spreading to my other veggies. What is a good home remedy to get rid of them?
Neem oil should help take care of the problem. Here is some information that may help: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
I have grown several varieties of squash from seed. Planted them in nice beds with much potting soil. Plants are flowering like crazy but will not set and bear fruit. Plants don't receive full sun until mid morning and the site can be breezy. I water every day and the ground is moist all day. I live in the desert of southern California. Temperatures now are reaching the mid-90s but have been 15-20 degrees lower before this.
This is common with squash plants. They produce male flowers before female flowers to make sure that pollen is on hand when the female flowers show up. The female flowers should be coming soon. This article may help:
https://www.gardeningknowhow.com/edible/vegetables/squash/squash-blossoms-falling-off-vine.htm
My new squash plants are wilting. Why?
It sounds like transplant shock. This article will help you:
https://www.gardeningknowhow.com/plant-problems/environmental/learn-how-to-avoid-and-repair-transplant-shock-in-plants.htm