You only get the +2 when editing a post that is not your own. "Post" means question or answer. You can not edit even your own comments after a certain window and you can never edit someone else's without being a diamond moderator.
The most reputation you can earn for edit suggestions is 1000 reputation - and you don't earn any reputation for submitting post edits after you earn the edit privilege at 2000 reputation. So, unless all someone does is edit, they usually reach 2k long before they hit that 1k rep cap for suggested edits.
In addition to posts, you can suggest tag wiki edits which are also worth +2 if accepted. You can actually continue to earn rep for these edits long after you've reached the post edit privilege because editing tag wikis doesn't become possible without review until you hit 20K.
All of this and more can be found in the edit suggestions FAQ.
You're asking about editing but mention deleting, so I'll venture there - yes, if you delete a post, you lose whatever reputation you had gained from upvotes and gain whatever rep you lost from downvotes. Note that you can not deleted a question that has been answered if that answer has a positive score and you can not delete an answer that has been accepted. It's also worth noting that if you delete very poorly-received posts too much, and you have no other good posts to balance them out, you're at risk of getting a question or answer ban. If at all possible, you should attempt to improve your posts, rather than deleting them.
Comments don't affect your reputation at all. You can neither earn nor lose rep through a comment.
The "edit but don't edit too much" can be interpreted a few ways. If you're editing a post just to make it visible, that would be looked down on. Too many edits can be annoying. But, if you're editing someone else's post, you don't want to be too heavy handed with the editing as you may change what they are saying. I'm not sure which of the two (if either) is intended.
Editing judiciously can bring posts to attention, particularly on sites other than Stack Overflow. Many users rely on the recent questions for their site browsing, and edits bring those posts into the active page and may earn votes or (if a question) answers. Again, making minute edits merely for the purpose of bumping the post isn't a great idea.