I want to send my Max patch to someone else, and I'm wondering if Max will include all my abstraction subpatches along with audio files used in the patch into one big file or a zip file. Or, do I have to do this all myself, manually?
You probably want to build a collective, you can include all the abstractions, third party externals, images and audio files you want in one place without the recipient having to do any work. Have a look in the help docs.
as far as I know, the best thing to do is to send a folder including all abstractions and audio files. the recipient will then need to put this folder in their max search path (ie: cycling74_patches_sharingcaringmaxpatchgifts)
I believe that subpatches will be saved as part of the parent patch automatically but if there are any 3rd party externals or abstractions they will need to be included in the folder.
If you want it to be editable you should follow Tim's advice and shove everything you need into a folder and make sure it is added to the max search path (in preferences). This can cause problems with naming issues though, for example if you include an abstraction that shares a name with one the recipient already has in their search path.