Pneumatics, etc
Yes, lot's to answer here, but I'll throw in my 2pence worth:
Bleed air for leading edge heating is indeed blown into a cavity behind the leading edge devices. It vents overboard via rectangular cut-outs on the underside of the wing, just behind the leading edges. As a result of the design, wing anti-ice is ineffective with the leading edges extended (flaps 1 and greater).
Catalytic converter? Not sure about this one... Not in the engine pylon/cowling, that's for sure. However there may be one to process air for the cabin, downstream of the a/c packs. At cruising altitude, perhaps adding ozone to the atmosphere is a good thing?
Regarding heat exchangers, yes there is also an air-to-air exchanger in the bleed line from each engine, located in the cowling (or perhaps the pylon).
Batteries: yes, two onboard. One for the aircraft (located in flight deck), one for the APU (located in the APU compartment, forward of the turbine, and heated by a thermal blanket).
Yes, there are inverters to produce AC power from the batteries. They power quite a few items, best to check your manual, as exact details will differ by model/customer preferences.
No, you can't separate DC busses on the overhead panel. Well, not without pulling circuit breakers anyway!