Ah, for the first one I forgot I left it like that. I changed it to a regular EntityItem to see if it would work after it crashed when using my custom one, and it still crashed while returning the regular EntityItem.
The second one I just fixed. I was using renderSnowball to render a projectile, and I figured out that it only uses the default texture file and not one from its arguments, so I copied it to a new class and changed its texture file.
For the third one, I'm still not too experienced and don't know what you mean by using packets. Also, could you suggest a better way of doing the code if it doesn't work on servers? I'd prefer it to work more like pistons or maybe sand/gravel, but haven't really been able to figure out how those classes work...