I could have written this post. I am currently 5dp2dt for the same reason, only 1 fertilized. It's devastating and I totally understand your fear, I'm so sorry this happened. I had never even heard of a 2dt until this happened to me and we were very disappointed.
The only comfort I got out of the whole experience was knowing that it doesn't matter when they put it back. If they put it back on day 2,3 or 5 it was going to work or it wasn't. It's very hard to not have more to pick from or put back, but there is no question, it is better inside of you than a Petri dish in the lab. Hang in there, it's not over.
I agree with all of this. As you see I just had one embie also. I did a 3dt but I don't think it matters. If an embie wants to make it I think it will do just as well if not better in an early transfer. Your ute is better than a Petri dish.