1.) There are many ways to cull. You can feed to a carnivorous animal or fish. You can use clove oil. You can freeze in ice cold water. You can hit on the head with a hammer, though that would take FOREVER for each and every one.
2.) Mason jars are those ones that stores sell in 24 packs. You need to make sure that you get the right size, though. They need to be large enough for a fish to comfortably swim around. Usually one quart is the easiest to find, but if you can find something bigger then that would be even better.
3.) You can use fake plants for spawning and grow out. Most will leave grow out bare though, if live plants are not available. Live plants have many benefits including fry's first food: infusoria. For the spawning tank, you will want to make sure that there are plenty of hiding spots for your girl, since there will be much chasing/nipping involved.
4.) I have not been able to find the cultures that I want at my LPS, but I found bbs there. Ebay is a great place to go, but there is also the classified section on this forum. Many members sell their left over eggs, cultures, and plants to other members.
I want to breed, because I'm simply interested in the whole process. I enjoy genetics, animals, and feeling accomplished (who doesn't?). I really want to make color combinations and lines that are not only interesting to me, but also other people. I eventually want to show my work, but not until I have something that really makes me go: WOW.