No it will not as this is designed for a 9mm caliber.
Aero Precision states the Aero Precision EPC-9 Threaded Assembled Upper Receiver and EPC-9 in general are compatible with some parts from other manufacturers but recommends using all Aero Precision EPC-9 parts to ensure proper function. I recommend contacting Aero Precision in regard to the Aero Precision EPC-9 Threaded Assembled Upper Receiver and the CMMG RDB BCG.
The Aero Precision EPC-9 Threaded Assembled Upper Receiver is compatible with most handguards that fit Mil-Spec receivers. So the Strike Industries Handguard should work.
Yes. The upper works with either 9mm or 40 S&W parts.