Pot size: 6cm
Give water at summer time / growing season only when over half of the soil is dried out. Ceropegia goes dormant at winter, so let it dry completely through the pot between watering. They are sensitive to root rot and overwatering so don't ever give water "just-in-case".
Misting is not neccesary.
String of Hearts likes light. Some direct morning sun is ok, but not whole day.
You can give some really light liquid fertilizer during growing season. Once a month is enough and give max. half dosage what is recommended on the bottle for other house plants.