Rich LV 6548 Grid charging

My system/ goal is primarily to offset electric bill and emergency power for whole house - I am running dual 6548 in parallel split phase, back feeding the main panel ( with the proper interlock) and right now it is set for SBU but I do not have the utility part wired. All working great. Obviously I cannot do any sort of bypass/pass thru but want to run the AC in ( grid to inverter) to charge batteries when required. Question is will I have to always worry about making sure this breaker open when in inverter mode running off PV and batteries ? Or does the unit realize the source is it's own output and ignore it until the the output breaker is opened and grid main power comes on?
I have a sub panel mounted in the adjacent stud bay and was thinking of wiring the inverter AC input to that box ( inverter AC out runs to main panel) In regards to the whole N-G bonding mess which panel would be safest to run it to?

Good question, did you get it figured out?.