My opinion:
First, no-one should include ALL their chat history. IRCC says 10 pages max, I think.
Second, go through first time filling out and collecting but including only the basics of what they ask for (that you have). THEN, go back and read over your app and see what you didn't have/couldn't include, and if there are / appear to be any gaps in the basic story.
In your case, based only on what I read above, you MIGHT conclude that there is not much info about your relationship before you started living together, and you've only been living together for 3 months, so perhaps that's thin. If so, THEN think what you could provide that would be best to supplement. If you met online and never saw each other until september, chat history would be pretty important; if you met in person and visited each other in person a lot before you moved, pictures and that stuff would probably be stronger.
Use your judgment as to what makes the best case for you, WITHOUT snowing them in with info. Just what you need to fill the gaps.