Pugilist
You didn't wait long enough. They tell you in the instructions to taste it before doing any bottling. If its not clear and tastes yeasty or sweet you're supposed to wait. You can wait up to a month without getting yeast bite.
I use a bright pen light to look for yeast sediment & bubble activity. If its clear, sediment at the bottom, no bubbles, waited the minimum days, I'll taste it, if not I'll wait.
I have never had to go past 2 weeks. This is with the mix & unhopped extract plus adjuncts, honey, fruit, etc.
FYI - The booster in your first batch is a blend of corn sugar (dextrose) and malto-dextrine. No table sugar in it at all.
I have made several descent batches with Mr Beer. You can get good beer with the kit, but the full blown boil kit is the way to go long term. The full blown kit will open up many new opportunities that don't exist with MRB
Several people in my homebrew club are astonished on the fact some of the beers are MRB. They were pretty good. Everybody loved the Octoberfest. - Vienna Lager Extract + Amber Extract, 1/4 oz of dry hopped Liberty.
If Mr Beer teaches you anything worthwhile it would have to be patience.
- Carb your beer at least 2-3 weeks before chilling - The instructions say 7 days, its not long enough!!
The all malt kits you got for xmas will make good beer if you let the yeast do its work. Just wait it out.
If you have questions with the future batches shoot a private message this way. I'm usually online everyday unless I travel for work. The reason I say private is so I'm sure to see it. I check general discussion section daily too.
Welcome to the new hobby.
Schlenkerla