I am not sure about the questions on plants, but I believe many people use florite as a substrate since it helps the plants grow. I am definately NOT the expert in the least on plants.
Betta fish do need a water temp of 75 to 86 degrees (according to aboutfreshwateraquariums.com). I have an eclipse 3 myself and I use a 10 gallon heater from Walmart. It works well and is hardly ever on. I put one of those 'stick on' thermometers on the side of the tank as well to keep track on what is happening.
Oddly enough, while searching for the required water temp of betta fish, I stumbled upon bettafish.net, apparently the 'official site' of the species and found that nearly every picture on there is of a betta fish in a vase or small glass. Unbelievable. This fish is getting such bad press.
For the record, no, I have not bred betta fish and dont really have the room, money, or courage to ask my wife if I can get another tank right now. There is some good breeding info at this site though:
Siamese Fighting Fish (Betta Splendens)