For water, just give your snake whatever water you drink yourself. Tap water should be fine in most places. Bp nutrition is really simple because they eat whole rodents, which means they everything they need in one furry package. You don't need to add extra vitamins minerals or supplements to the water. If the prey was healthy, it is a balanced diet all by itself.

Your track might be scary for a baby that has only lived in a tiny tub before, but you can make it less so by cluttering it up with extra hides, fake plants, etc, and by covering the back and sides with paper or cardboard to make it less exposed. A baby should be fine in there as long as it has plenty of cover.

How much heat you need will depend on the temperature of your room, so the only way to know is to plug in and find out, then adjust as necessary. You don't need a separate day/night bulb; if there's a window in the room the snake can tell when it's day and night, and will sleep in a hide all day anyway.

For humidity, the first thing to do is cover up as much of the screen lid as you can except for where the light fixture is. If you only use one bulb on one side of the fixture you can cover even more. Aluminum foil works well for that. There will still be enough ventilation, you just want to keep the humidity from escaping quite as fast. After you've done that, see where you are and if you need to do more, such as misting or adding sphagnum moss or a humid hide, etc.

Keep in mind that your needs for heat and humidification may change as the seasons change, and you'll find that out as you go.

Make sure you use a thermostat with your uth, don't put very much substrate over top of it, and make sure that the surface of the glass never gets too hot even if it's covered - sometimes snakes dig down and then get hurt.

Good luck! 😃