Just in general, for products you might use in the future, they have the active ingredients on the package which you can then look up on the internet, no need to entrust your family's health to a random store associate.

Below is a site that has info on some products:

Here is a link that might be useful: MSDS

15-0-0 is the fertilizer analysis. You will see 3 numbers in that format on most every fertilizer that exists. The first number is the percent of product by weight that is Nitrogen, the second number is Phosphorous and the third Potassium (sometimes called Potash). For lawn fertilizer all you need is Nitrogen.

Phosphorous has a potential to leach into water sources and contaminate streams, so it should only be used when you actually need it to get results. Potash isn't bad for anything, but it also doesn't do your lawn much good, and over-applying encourages dandelions.

As to Weed and Feed, it contains some Nitrogen, which will make your grass grow in thicker and greener, and also 2-4D. 2-4D is one of the most common herbicides in the world, it specializes in exterminating broadleaf weeds (dandelions, clovers, etc.) without harming grasses. Applied even close to to directions, it should remove most lawn weeds without harming your grass. Be careful when you get close to any flower beds or vegetable gardens though, it has a potential for going a little past where you were aiming, and some species of plants (especially vines and melons) respond VERY poorly to 2-4D.

I wouldn't call it 'totally safe' for people, but as herbicides go it's pretty safe. Give it time enough to dry on and soak in, then you're fine.

Some people think plant poisons such as those containing 2,4,D, Dicambra, and the others are not much of a problem while others think they are too dangerous to use. The Province of Ontario has banned the use of them for a reason.

Here is a link that might be useful: Problems with 2,4,D

Well, the only thing wrong with dandelions in the grass is if the sight of them truly bothers you, or just that someone said they're not supposed to be there. Someone who doesn't want to come to your yard and pull them out, but make a profit off of telling you they shouldn't be there, then offering a product that kills them.

I just applied the EG liquid weed and feed. How long should it be before I see results?

What results are you looking for? The plant poison part of that weed and feed should start showing dead plants in about a week while the feed part may start to show up in a couple of days with a greener turf, depending on temperature, rain and other environmental factors.