In terms of what the OP likely cares about...

1. Scrip system is an excellent way to level (that's probably what you care about). You synth an item like you normally would, but before you start, use collectable synthesis. The items you make won't stack. Only make collectable stuff when Rowena's turn-in people actually want it. (Ctrl-U on PC to check). The exp bonus is pretty huge. I think it is safe to say that about whatever you'd get for exp for the synth, you get 4-6x more on the turn-in.

2. No idea how to help you there. I'm not good at figuring out CC if you don't have them all at 50. Sorry ;;

Another thing to keep in mind about collectable turn-ins. While the exp for a level 51 synth may stink when you are 58, the exp bonus from the turn-in is still the same. So, when you do this, find a synth that is _cheap_ to make. And just zerg that.