1. the stem should go about an inch or two under the water (if it doesn't go under the water, the smoke won't be filtered)

2. Not sure how much it would cost. Never bought that from a hardware store.

3. It could possibly drill a whole in steel. Never tried, try it out and see.

4. Bongs don't use carbs like pipes. There is no hole to cover and release. Bongs use sliders. When you want the air to come in and intake the smoke up to your mouth to inhale, simply pull the stem/bowl out about 2 inches. It's easy.

Grape juice doesn't taste that great. I tried it and i didn't get as high as i normaly did. Orange juice though, i dont know. Let me know how it works out for ya.