Dimming stat is better if you're using a normal light emitting bulb (just dims the light when the right temperatures are reached then fires up the bulb again when the temperatures get low). You can still use timers etc with thermostats, it'll just switch the thermostat and lights on at the time you want. You can use the day/night ones but I've never used one so can't help with that!
Yeah you can get the sand from toys'r'us.
Sounds like he could see his reflection and wanted to pick a fight, they're not so smart
that kind of behaviour towards Lilo could be dominance or mating behaviour. Now that he's not trying to pick a fight with himself he may be directing it towards her. Whereabouts is he nipping her?