How many amps is that timer rated for? Watts aren't a good measure, you need amps. It looks like you could have overloaded stuff - it's not a good idea to use outlets for your grow if you don't know what else is on them. I'm glad to hear all is well though. thank goodness.
There is a safe amount of "draw" that your outlets/power box can handle. For example, code requires homes to have a min. of a 100amp main electrical panel. This means that the total load is 100amps. On the rest of the panel, there are breakers rated at 20 amps, 30 amps, etc for your stove, clothes dryer, lights, heat, in all different rooms. These ratings mean that each individual circuit can only use a maximum of said circuit. If you try to draw 21 amps of a 20 amp circuit, it trips.
There is however a safe load, which (please don't quote me) is I think 80% of the breakers limit, as a general safety rule. I think if you've been riding on the fence, alot of heat will be generated, and could have the cause of your meltdown.
1000w ballasts use twice as much amperage at 120v as they do at 240v, which is why people prefer them. You can attach more to a circuit at a time safely. Digital ballasts are a little better as well. (you could run 7 digitals where normally only 6 could be run)
If you've got a 2 rooms, with 2 outlets, they very well could be on the same circuit. Individual outlets won't matter much when it comes to total draw. Me for example, am lucky enough to have a decent breaker setup. 1/2 of my room shares the bathroom circuit (and we don't use hairdryers, bonus, cause they're high amperage), the other 1/2 shares a totally unused 20amp. This is where I will plug in my 1000w (we've got pretty well the same equipment)
When your lights turn on, at your electrical panel, does a particular breaker start to Hum or buzz? This could indicate an old breaker that is failing to trip properly and should be replaced. You also could possibly upgrade the breaker from 20 to 30 amps to handle the extra load.
But please note i'm not electrical expert. I'm just passing on what I know to be true and (where stated) a little guess work.
Keep us updated man, and good luck.
PS - I just noticed the part about mapping out your circuits. What you want to do is turn off all your sensetive eq. like tvs/computers etc. Then, one by one, turn off a breaker to see what it shuts off. Alot of them are labeled by the electrician. (i've never had a house that wasn't). Some will be for lights in multiple rooms, some for plugs. Some will be for baseboard heaters, dryer, stove, water heater (but those will be the honkin' big breakers, the 30amp guys, w/ 2 switches together.) Once you knock off the larger guys, depending on how big your house is, it'll take some effort but its well worth it to know what goes where. Hope this helps!