Such good news. It makes me feel so good to hear about Harry. I agree, though, don't be surprised if Harry is a girl. I don't think I've ever seen a male calico. I guess there's always the first time.
One thing about his lack of potty, when kitties are small, the licking of their mother stimulates them and makes them go. I don't remember how old they are when that stops. My Leonardo was a bottle baby...only ten days old when he was abandoned on my doorstep. The vet had me use a damp cloth to rub him like his mother would if she were bathing him. That was almost 12 years ago. He's a healthy 13 pounder now. The vet should be able to fix him up fine. Just stand back, when he goes, he may really go.
GOOD JOB!