Stupid exhaust question and story.. pics!!

[Tantwoforty]

So i have a cat back...
And when i got it it sounded great.. it was loud but tolerable.. great tone.
Then this happened...

also this


Now think of the pretty purple is flaming hot red... and say to yourself how much my camera phone sucks.
After this happened and i got it all fixed and running right again, a few things have changed..
It melted my gaskets to a fine powdery crisp.. it raped my nice new cat i recently bought to pass smog.. to be more precise it deformed the screen closest to the rear of the car, and turned it sideways so its free to rattle its little heart out.

So i picked up some new gaskets.
I removed the remnants of the dislodged screen inside the cat and left the front one there since it has no problems.
Then i reinstalled the cat back.
When i started the car it was at first pretty pleased since the massive leak from the flanges was fixed and my car didn't sound like a wet paper bag anymore.
but then it settled down to idle and started rattling.. like a loose screw noise. so i checked it out and came to the conclusion that its inside the muffler. so i drove around and the sound is like 70% louder then before. and rattles!
I am assuming that a piece of the cat fell into the baffling and is stuck..

So my question is would overheating and shooting raw gas and flames out my exhaust melt the packing in the muffler and cause a large sound increase?
and would buying a new muffler of the same type and welding it on fix this.. or would not replacing the resonator mid pipe at the same make it kind of pointless...

any input is helpful, i searched and didn't find anything quite like this...