Glad you are getting on with your setup which sounds very cool. Nice one, seems nicely set up for Studio and Live work and thanks for posting your solution. Live as master clock I think is the best route.
My setup is not dissimilar to yours. I'm working towards some live stuff this year and have always been keen to play my studio work out.
When the RC-505's came out I saw the opportunity also. I was thinking about an OctaTrack but really dont want to mangle loops live, the RC's effects and simplicty appeals.
I'm planning on loading the RC's (I have 2 and will work with my mate as a duo) with 16 bar loops that make up my tracks. Along side this we'll have an EMX-1 for drums running through a Korg Kaoss Quad. Along side this will be the iPad, (run through the Duo ex) and an Elektron A4 both for improv noodlings.
All of the clock feeds come from the Acme-4, so its all in sync, no computer! The Acme allows very cool swing and half/double time tempo variations on the fly. Very powerful central unit.
All this running into a Mackie 1402 VLZ3.
Final item in the setup is an RMX1000 which is setup on the mackie on the alt 3/4 bus. This become active on the mute button on the mixer, so to send any channel to the RMX (which is fed back into the mixer on its own channel) I just need to hit mute on the mackie. Works well. A bit of tape over the mute button on the RMX input channel prevents accidental feedback send!!!!
Good luck with your musical journey my friend...