Great that you found duel boxing fun. Though I doubt you are the first on your server as a lot of people do this, they just don't call it dual boxing.

1) I doubt /castsequence will work as one is a /cast and the other is a /use. Look into the mod "Autobar" it lets you do this and allows you to assign a key to it.

2) Never heard of two box tool kit but follow is easy. Do as the man said above.

3) There are no looting macros and none are possible. Only suggestion I would make is turn on auto loot, this just takes all the stuff and puts in your bag AFTER you right click on the mob.