I'm a US Outland as well, and after reading this I think we may have included too much! Wish I had found this forum sooner, haha.
We included:
1. around 100 Photographs, printed on photo paper and then taped 2 per page to computer paper with descriptions & dates. We did these in chronological order and added captioning that kinda showed how our relationship developed.
2: Personal Communication: a few pages of holiday cards and poems/love letters we'd written each other, drawings I made for him etc. more mushy embarrassing stuff
3: Sponsor's Personal Essay: my husband wrote an essay from his point of view describing how our relationship developed.
4: Reference Letters: I believe the US checklist asks for at least TWO of these... Affidavits from friends and family regarding relationship. We included one from his dad, one from my mom, and a few from close friends.
5. Proof of Travel: Plane tickets, hotel receipts, spouse’s passport stamps, etc. (included joint travel together to visit my family)
6. Joint Leases - we had two previous leases, and one Affidavit of Residence letter from our current landlord, in place of a formal lease.
7. Joint Financial Documents - a signed letter from the bank attesting our joint checking account.
8. Tax Assessment from 2014 which shows that my husband Filed Common-Law.
We did not include any chat logs or phone bills. We no longer had access to chats from before we lived together, and now that we live together we don't have many. We called Virgin Mobile to request our phone bills for the past 3 years but the phone company said it would be upwards of 5,000 pages and all the texts just say "Virgin to Virgin Text Message", we didn't want to kill that many trees just to prove we call each other. We hope that our other proof will be enough.
Also I read your post about waiting longer in regards to FBI and medical submission - We sent our application without an FBI Background Check because of the long processing times, planning to send it in once we get a case number. This is becoming more and more common with all the FBI backlog so I'm hoping CIC accepts it. You can send it in without these and just add them later or when requested, from what I know. Good luck!