Trying to package a prefab for sale in asset store

I am new to the Unity publishing side of things. That being said, my new asset is up to the standards that I would like to try to publish it on the store. I have encountered a few issues, however: 1. Unity asks users to test their prefabs in other versions to see which will work (I completely understand the need for this). I am using Unity 5 and am trying to export the prefab so I can test it in other versions. 1a. What I have found, is that it wants to upload EVERYTHING in my project. I tried to do this by de-selecting what I didn't see a need for. This did not work at all when trying to import it into unity 3. 1b. I tried to do this as the upload tool saw fit (exporting everything) and in Unity 3, I immediately got a message that one of my scripts (very basic, for opening a door) could not import.

1. Some of my prefab does not save properly in the prefab.

2a. I was at first, having issues with textures not saving. After a while of just retrying, it seems to work.... odd. 2b. I have a mesh collider set as a trigger for the function of my doors. All of which seem to be fine, except for one. This particular one, resets to the exact size of the door every time I save it as a prefab, and when opening the prefab again (even in the same scene). This would be an annoyance that I would not expect potential buyers to appreciate when attempting to use my asset.

1. Lastly, how should I have the files, textures, etc. arranged for the easiest experience for both myself, and potential buyers?

As I said, I am new to this, so I'm assuming there is a simple solution to all of these questions, and I appreciate any and all feedback. Thanks!