Backtagging: Yes please. I'm slow and often have to stop threading for a few days, so if you're willing to backtag CR will be much easier.
Threadhopping: Yes. I love it! If something in another thread sparks your characters' interest, please have them jump in! Just don't be surprised if Tyki jumps back. ;)
Fourthwalling: Please contact me.
Offensive subjects (elaborate): I'm hard to offend. If something is getting to me I'll let you know.