No they won't. Snails would be fine.im sure snails will be eaten.
A green terror should not be fed other fish. They are a very small part of their diet in the wild, and there is no reason to give them live fish. It may cause more harm than good in the long run. Feed a good cichlid pellet, and give it frozen food as treats occasionally.
There is also no reason for dither fish. A GT is active enough and will not want the company of smaller fish if not kept in a much larger tank than a 55 or 75. Just keep your GT by itself. If you want some snails those would be fine. Just make sure you feed them and that they have enough calcium.
All of this has been covered, several times in this thread. Why don't you go back and read your thread and you will have all the answers you need...