I would make sure the groomer knows about the sore ribs and the heart issue so he doesn't get more injured and if he gets too stressed they can stop the grooming.
I would definitely notify the rescue then as they may want to bring charges against the breeder.
If you wanted to put him on a better quality of food that is usually an advantage for healing and recovery. Pet supply stores carry foods such as California Natural, Merrick, Blue Buffalo, Chicken Soup for the Dog Lover, Dick Van Patten etc and you might find it will help him to have a good diet.
Pedigree has a lot of fillers and preservatives in it in comparison to the more premium foods.
How he can do and how long a life he will have is a big variable. He may not be as active as a normal standard poodle would be (this could be good - standards are *really* busy dogs!). He might die younger than a healthy dog would but you can't predict that. I had a dog with a 5 out of 6 heart murmur live to be 16 1/2. I've also lost a dog with a mild heart problem at age 9.
If he is positive for heartworm for example treating him may make a big difference.
I've also had a couple of dogs who lived into their early teens with the help of heart meds. You just can't tell. I wish I could. The cardiologist might be able to give you a more accurate prognosis after a full exam.
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