Skittles, it's great to see someone so prepared! With the Sterilite, you may not need to raise the humidity at all for shed time, but if you do, there are a few easy tricks you can use: switch to a bigger water dish for duration of shed, move water dish completely to warm side, add 2nd small dish or any other source of humidity (such as a sponge that you run through the dishwasher every day or two), or create a humid hide (my current favorite method for this involves using a coconut fiber hanging plant basket liner cut to size and turned upside down over a water dish, with an entry hole cut in).

A human heating pad should be adequate for heating the enclosure, but you may find you need to put it on medium instead of low for one that size -- just make sure your substrate is thick enough to avoid too hot a hot spot. Brand isn't important. The heating pad can touch the container, but you do need airflow either above or below the heat pad. The easiest way to do this is to use the stick-on feet for furniture and electronics that you can find at WalMart or any hardware store, but anything evenly-sized that won't let it slip around will be fine -- you can use paperbacks if you want, as long as it's on a snug shelf or something.

Just make sure you set it up completely and give yourself a couple of days to get temps and humidity right (wait a few hours between adjustments to give it time to stabilize), and you should have a great set-up.