I'm not sure that it is possible to overfeed a flytrap, but traps usually die after 5-6 bugs - sometimes sooner, so if you keep feeding it every time a trap reopens, you will have one boring looking flytrap (I guess you could call that overfeeding it)
Can they live inside? Well that depends on your setup. Generally, they do better outside in full sun, but if you must keep them inside, give them as much light as possible. One guy posted a picture of his terrarium where his VFT's were absolutely flourishing. I'll look around for the thread.
No, I don't think you can overfeed a VFT, but if you are constantly triggering traps, I've heard that it can stress the plant.
Yes, you can grow them indoors, but as twigs said, they usually do much better outdoors. A sunny windowsill or a good growlight will work, but you'll probably struggle with providing them with a good dormancy.