Another small victory…
I can confirm that if your check valve off the front glad hand is full of crud and gets stuck open, the parking brakes will not release. Thanks to
@Ronmar video I was able to get a better understanding of how all that works and because I will be deleting the front glad hands anyway I removed and plugged the emergency glad hand feed line from the 2 way check valve under the cab and then capped off the faulty check valve behind the bumper. That fixed the issue and now by brakes can release. I’ll hopefully get to fully remove that system this weekend.