A Ceramic heat emitter is a ceramic "bulb" that only gives off heat instead of light. I use a flucker's clamp lamp with the dimmer and I hang it over the tank so it doesn't get too close (these things get HOT). But they do sell stands for them as well.
I just grabbed a 98 cent spray bottle from the cleaning section at walmart. That thing has some high output! Lol.
I would highly recommend the larger exo-terra. WTFs get pretty big and 4 of them are going to need as much space as possible. Exo-terra is your best quick and easy option IMO. I'm not sure what other options there are, besides making your own.
I just take the plant out of the pot and thoroughly wash the whole plant including the roots and then plant it directly into the eco earth. This works best with a false bottom since it prevents standing water from accumulating bacteria in the substrate. But for now since you probably want to keep the plant potted in the current set up you can just make sure you cover the soil in the pot really well with eco earth and wash the plant off really well before putting it in. There are other things you can do with layering substrate and using special potting mix etc but I don't have much experience on that end.