Welcome.
To answer your questions:
1. Light: Your plants will need much more light that what you're currently providing. I suggest buying two workshop light fixtures from Home depot/Lowes and put a 25W cool white compact fluorescent lightbulb in each fixture. This is probably the minimum light level you'll need unless you supplement with sunlight.
2. Air circulation: First, there are two types of terraria--ENCLOSED which have a cover and OPEN which don't have a cover. Most people have enclosed terraria because this typically allows for higher humidity which helps some species of CPs grow well. However, there are two disadvantages to enclosed terraria--stagnant air and high temperatures. Your plants will be at GREAT risk of fungal infections if the air is stagnant. Most people use a small AC computer fan (Radioshack, $10-20) to circulate the air. Circulating the air in an enclosed environment will not change the temperature or humidity.
3. Humidity: Many CPs do not require high humidity to grow well and will do just fine at levels tolerated by typical houseplants (40-60%). However, if you heat your home in winter and/or if you grow certain CPs you might want to increase the local humidity by placing them in an enclosed terrarium and/or putting them ontop of a wet gravel tray. Nepenthes usually don't like to be in water for a long time, so keep them above the water.
4. Heat: Most CPs don't require high heat to grow, and in fact, many like periods of cooler weather. So don't worry about not having "baking" temperatures.
5. Water: Make sure you water your CPs with distilled/RO water (you can buy at grocery) or rainwater. Do not use tap water--most tapwater is unfit for CPs.
6. Feeding: Some people feed their plants with bugs, others like myself spray their leaves with a diluted orchid fertilizer, but you SHOULDN'T spray fertilizer on sundews or butterworts. Regardless of what you use, most people will agree that feeding your plants makes them healthier. One thing--unused bugs can grow fungus in an enclosed terrarium which may spread to the plant, especially those that are prone to rotting (butterworts, sundews).....so if you use bugs you might want to pulverize them into powder and feed them a little at a time.
7. Soil: Looks like your plants are in long-fibered sphagnum moss (LFS). If so, you probably don't have to repot. If you bought them from home depot/lowes, you probably want to think about repotting them into something better. Pure LFS works well (you can buy this at home depot/lowes) for your sized plants.
8. Aesthetics: Some people like to have their plants in a fancy-looking tank/setup. Others don't care and put all of their time/effort into the plants themselves and don't care about how the tank looks. Others are in between. As long as you provide good light, good air circulation, decent humidity, good soil, and distilled water, your plants should do great.
There's more to be said and there are exceptions to every rule, but I think this will give you a good place to start.
Good luck.