When I phoned to make an appt for Missy's 2nd set of vaccinations, I asked about dog food. They said Science Diet is "Great Food" and to continue feeding it to her

Don't worry, I didn't...I've switched her over to "Go Natural" and she's doing wonderful with the switch. Tomorrow will be her first day of only having the new food, I took a week to switch her over. I think it's crappy that my vet recommended it though.
Well, just now I called the office again to ask them about Nutracal (well the Canadian equivalent called Excel), which I've been giving to Missy when I've noticed her getting some of the early signs of hypoglycemia. They told me NOT to give it to her, "her food should be giving her enough nutrition". It is obvious to me that both yesterday, and 2 days prior to that, Missy needed the Excel. If I wouldn't have given it to her, I think things would have gone downhill. She is only 8 weeks old now (7 when I got her) she weighs 1 lb 3 ozs as of today. She was obviously sent away from her Mom to early (not by my choosing). Both days that she had some troubles (became tired and wobbly, and not eating much) the Excel pepped her right back up, and got her eating and back to her regular old self. I told the vet office this, and they still insisted that I shouldn't give her anything but her dog food.
I'm not sure what to think of all this. I'm kind of getting discouraged with my vet, whom I always thought was wayyyy over priced, and went overboard with some of the things they had me do with my previous pets. Maybe it's time to find a new vet. This one is suppose to be one of the top rated though!
So about the Excel (or Nutracal), I've been browsing the forum, and some places I read to use it a couple of times a day, as a preventative type measure, to keep her sugars stable...and other places I read to only use it when she seems to be not doing too well.
Please, do you have any tips or suggestions to keep Missy strong and healthy through the next few weeks when she is SO little? I've been researching here like crazy, but I get such a mishmash of information. I would appreciate some opinions on foods, supplements etc. I've been mashing her food up with warm water, and mixing just a smidgen of canned food of the same type, just to get her interested in eating. I've been giving her the Excel 2-3 times a day, and she has a warm water bottle, and a space heater to keep her cozy. I'm making sure that she gets her rest and keeping her stress level low. I just want to make sure she makes it through these next few weeks. When I see her starting to slow down, it REALLY worries me. It's happened 2 days out of 6 so far.
Thank you.