My Halle had a singleton puppy her first litter in 2009. Halle is in the 6lb range and I wondered for the longest time if she was pregnant or not.....even though I knew she was from an early ultrasound. Even after the x-ray...some days she looked PG and other days she didn't. It wasn't until I saw movement that I was finally convinced. When we had the xray done, the vet came in & told me "we have one very large puppy in there"..........................scared me to death! Very large puppy??? Was she going to need a c-section......should we try to free whelp????? Well yes, they did indeed say to try having it the natural way and thankfully she did whelp him on her own. He was fairly big and she did let out a yelp when his head popped out; he weighed 6 3/4 ounces at birth!!
Anyway, once the singletons are born, there's not much difference in caring for them compared to a litter of more. The singleton's usually gain a bit quicker since they've got mom's milk all to themselves. My only concern....not really a concern, but more of feeling sorry for him.....was when he got a bit older & mom doesn't spend every single moment with him anymore. I wondered if he was lonely or cold. We kept a snuggly soft stuffed animal/toy or two in there with him and of course spent as much of my free time with him as I could. He was a very well socialized little boy by the time he went to his forever family.
Good luck with your little guy!!