+2 On getting a new pack. If your current pack doesn't have attachment points on it, it's inadequate and needs to be replaced. Consider getting one of the heavier weight Space Thermal blankets to put on the floor of your tent, under your closed cell pad. That will greatly reflect heat up to you and keep the ground from absorbing it and chilling you to the bone. Down sleeping bags are warm on top, but crush flat on the bottom and have zero insulating value.
If you stop, put on layers, but only a few. If you stay stopped long enough to get cold under added layers, you stopped too long.
Better to keep moving and not let muscles get cold. When you stop for the night, put on lots of layers after you set up camp. Setting up camp will generate lots of heat, too, like walking.
As for carrying stuff, the new pack should accomodate it. Or consider a haversack, shoulder bag, or whatever you want to call it, a possibles bag, for small stuuu that you want to keep handy.