A. curassavica does quite well indoors for the winter. The trick is to keep it where it will get some sunlight and to keep it watered. You should also consider potting your stems. We haven't had any reports of curassavica making it in water, which doesn't mean it couldn't happen, but you will have a better shot at keeping them alive if you put them into soil. They won't grow quickly, but they should make it through the winter. You can put your plants outside in the spring after the danger of frost has passed. My mom has done this the past two years and has found the biggest problem is their cat -- he keeps digging in the pots!
You don't need to sacrifice the stem with aphids. If you are finished rearing your caterpillars you can spray the aphids with hot, soapy water (dishsoap will work just fine), then rinse your plants. If you still have caterpillars you can also just squish the aphids, although gloves are recommended so you don't turn your fingers yellow.