You're worrying more than you need. You have good evidence already, simply build from that and prepare a good package. Being married for over 2 years is very good because you won't receive conditional residence. From what I've read, the presentation and organization of the evidence helps a lot, and it's not uncommon that young couples don't have property/assets. The fact you've been living together for 3 years is very strong evidence. You can also show documents from 3 years ago, etc, showing each of you lived at the same address, like old bills and letters, even if they're not 'joint'. You didn't mention, have you filed taxes together? That's pretty important. And check you are marked as Married on your W-4s

It's not too late, he can also still add you to all of his checking/savings accounts as a joint owner, and you can add him to yours, even if the accounts are 10 years old. Simply go to the bank and fill out a form. It helps because it shows you're willing to share your finances/earnings, not just a new account. I dont think you can have joint credit cards these days, only authorized users, the fact that you already added him is good and make sure you both use them. Add each other as emergency contacts with your employers. Some utilities only allow one account holder, so if takes over the electricity, you can take care of the phone/internet for example, so you'd have statements in each of your names with the same address

start building up a folder of all evidence you have and date it, photos, trip itineraries, bills, statements etc. I actually scanned everything so I could organize it on the PC and simply print my entire package. Hope that helps!! good luck!