Angels don't like hard water, they prefer soft acidic water. Most fish will do fine with a steady
pH. i prefer not to use chemicals to keep a certain ph just because I worry about fluctuations. Especially if you are not doing any water testing. But maybe if you're using a ph buffer then you are checking your ph. You don't need to do anything to make the water hard.
They don't need to be fed till they are free swimming. Not when they are still hanging off the leaf or whatever they are on but after they are actually swimming around. They are not eating the babies (but they might) when they put them in their mouth and spit them out. The parents are just trying to keep them all together so they can keep them safe. Are they in with the other fish or in a breeder tank?