I hope you get Scooter - he's sooo cute!
I have two terriers and they do keep one another company when we aren't around. In fact, if I take one somewhere and not the other, I get "the look" when I get back home, despite the fact that the dog left home had people to hang out with. They're still too young to try and handle two at once in a public setting and still get anything done (just over a year old, and energetic dogs).
Hopefully the medical condition could turn out to be something that can be lived with. One of mine has a heart murmur. That's a serious thing, there's nothing to be done for it - and the breeder disclosed it before I got him so I knew and didn't care (I was already attached). A previous dog also had a murmur and he lived a long and healthy life until he was nearly 17 years old.