Should I have marked it community wiki?
In short, yes, you should have done this if you wanted other users to be editing your post for content.
The idea of the edit system in SE sites is that when you edit any non-CW post, you edit it for everything but the content. You fix spelling, grammar, formatting issues, correct clear typos or minor mistakes but ensure that the intent of the original author is maintained. You shouldn't be adding entirely new content, or editing something that the OP feels is correct even if you believe it is not.
That's not all true of a CW post. For a CW post it's a way of saying, "other people can edit the content of this post, feel free to add entirely new tangents of information I left out, go into more detail for existing content, etc." Since that's what you wanted; for another person to be able to come in and add a significant amount of new content that you didn't have in your answer, you should have marked the post as CW. Also note that being marked CW means that the rep requirement for non-reviewed edits is significantly reduced, although in this case the user has less than 100 rep, so it would still need to be reivewed.