1. Please NEVER use anythign except what is advised by the manufacturer.
2. no idea
3. nope, but almost all info is now on this thread (too bad there is so much chatting and too many people who keep posting the same questions again and again)
4. it is a red sign (see pics below)
5. that is not the low coolant mark, it means the engine was cold, when the engine warms up the sign goes away.
6. no idea
remove the battery terminals for 20 minutes, it should reset the car. if not, take it to toyota and get them to reset the memory.
sounds to me like you have air in the system or old fluid. get it changed/bled correctly and have your brakes adjusted.
it has to do with the fact that the idle is artificially at that piont due to the choked engine. removing the cat will reset this problem eventually.
glad to know it is done, let us know what fuel economy you get over a long term
you can clean it with a Q-tip, just be very gentle. BTW you'll probably do a better job than the mechanic, and you'll NOT damage it. these mechanics are monkey with toolboxes, don't trust them. as for sounds, just fit a set of 5 -5.5 inch speakers on the rear shelf and enjoy the "fill". DO NOT fot anythign larger as it will make the shelf sag and will eventually murder the shocks of the tailgate.