You're set up last year is not a particularly warm sleep setup- I wouldn't really expect it to be comfortable below 35 or so to begin with. Pretty much everything has been said already but here ya go
- don't forget your head. A warm beanie or two, or a down hood goes a long way
- stoke the furnace. load up in calories before bed and if you wake up cold eat a candy bar or something.
- layer up. Wear all your warm layers inside your sleeping bag.
- keep dry. Moisture accumulates over time. Make sure you aren't exhaling into your bag when you sleep. Use a ground cloth to keep from wicking moisture up from the ground.
Bonus tip: don't sleep in low places where cold/damp air and dew settles at night.