As far as the carbonation is concerned, there is no reason to worry that you don't have enough viable yeast in the bottles. It's there. Don't worry.
It just needs more time. Chances are that this time of year, the spot you are keeping it is a little too chilly to let the yeast work as fast as it would otherwise. So, just give it a couple more weeks.
Also, when you want to try another bottle (or 3 or 4 or 8), make sure to give it some good fridge time. If you just pop it open after chilling for a couple hours, a lot of the CO2 will escape right then.
If you give it 2 or 3 days in the fridge, the CO2 will get better absorbed into the liquid and you will end up with better carbonation results. Believe me, it took me a while to learn this lesson and plan ahead for when I want to drink my beer. Just keep refilling the fridge as you drink, so there will be more ready by the next time you want some.