Re: so much for
No, it doesn't mean what you and Pedroski have suggested. It means exactly what Bob said above.
You use it sarcastically to mean "Despite your saying you were going to do something, you didn't." (Or: Despite your saying you were not going to do something, you did it anyway.)
It's also used when something fails or is broken beyond recovery.
So much for that egg -- after the egg falls off the counter onto the floor.
So much for that plan -- after you realize that the route you wanted to take is blocked by construction.
So much for a clean house -- after the dog tracks mud all over the place
The reason we are having a hard time explaining it to you in this context is because it makes no sense in this context! If it had been "So much for a clean kitchen!" or "So much for keeping things tidy as I went"" it would make sense.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.