It sounds like you still have some time left to make a few more good memories with Cody, then.
Just take it a day at a time. Once the radiology report comes back, you'll have a little more information to go on. Don't be afraid to ask your vet for advice, either--they can sometimes spot signs you might be missing. A good vet won't tell you what to do, but will give you the information you need to make the decision.
Listen to your head, but make your decision from the heart. There are no hard and fast solutions here. You can only do the best you can with the limited information you have. It will be the right decision.
And you're right--this absolutely sucks big time.