The Obesity Epidemic

I have a 4-year old female Beagle. The vet said she may have a slight heart murmur, and needs to be checked again in a couple of months. She also said my dog has an athletic heart. My vet also said that dental health directly relates to the condition. Is this so, and can you please explain what specific steps can be taken to offer the longest life possible for my dog? My dog is more than a pet. She's a family member. Thanks for your help!

We have a Wheaten Terrier named Jack. He is 2 years old. Our daughter is moving back in with us with her Shepherd mix, Dusty, who's about 4 years old. Both dogs have been fixed. Jack is okay with other dogs, but we have never had another dog in our house or yard. He barks if other dogs pass our yard. Dusty lives in the city and sees a lot of dogs. I want to make sure Jack and Dusty get along.  What do we do?