From the info you have laid out on what you have done to the EFI that all sounds good to me. I have never seen or heard of WiFi doing that using a BCM94360NG, It needs nothing added kext or patch wise too get it working and should just work out of the box....hhhmmmmm
Ive seen this exact problem tons of times using the Intel wireless card and the way to fix it on that is to shut down the system and remove the power from the wall, Wait a few minutes and then plug it back in and boot back up and hey presto but that's a intel firmware issue curtesy of the kexts and shouldn't be a issue using a BCM94360NG. hhhmmmmm again...lol
Have you disabled or made your own USBMap.kext for your board as my one is wrong for the X570-i?