hope this helps!

1) yeah that's about right. It might be 70% Cat and 30% muffler.

2) It'll probably be louder with just the straight pipe in. Why don't you try taking out the muffler but leave the Cat in or switch them, to see which one sounds louder.

3)Well you should try a universal muffler with a wide tip, like an SPP or HKS. The bigger the opening, the deeper the sound.