Apparently this is an issue with the SN30 Pro itself. I got it working. Here's what I did:
Deleted /etc/udev/rules.d/99-bluetooth.rules
Deleted SN30 Pro from registered Bluetooth devices
Powered on SN30 Pro with Start+B (Android mode) and held Pair button (top of controller) for 3 secs to immediately go into pairing mode. While in pairing mode selected
Register and Connect Bluetooth Devices in
RetroPie-Setup Script >> Setup >> Configure Bluetooth Devices
Selected
8Bitdo SN 30 Pro from list and finished config
Did NOT set up udev rule
Now the controller is working perfectly; I'm able to open Launch Menu or go straight into games ... no sitting at black screen for ~40 secs. Also no waiting required to navigate script menus either.
I did have to reconfigure controller layout ... and the L/R triggers are actually recognized now as well.