Sorry you are having sleep issues. I am also a stomach sleeper! I had anterior approach, so technically I can sleep any which way. I just need to be careful turning over, and back. I've chosen not to risk it, so far. Last night was the first time I intentionally rolled onto my right side. (I've been on my back, or on my left side with a pillow between my legs.) I was too nervous to stay in that position though. 6 weeks can't come fast enough!
Since the boys are now 6 years old, I am surprised the breeder is doing cadiac tests NOW. Wouldn't a breeder normally do that with a young cat just prior to starting it in her breeding program? That's how responsible dog breeders do things. With bichons (the breed I am most familiar with) they get eyes and knees tested and certified as clear of all genetic issues, prior to any breeding. The timing seems a bit odd to me.