A couple of thoughts.
Drill out the gas port. You have an adjustable gas block so you can close it down if your getting too much gas at a latter date.
Till you get the guns working don't use change more than one thing at a time. How do you know what made things work or worse if you are changing more than one thing at a time.
Dip your BCG in a pan of Mobile One motor oil overnight. Then just wipe off the bolt face and shoot it.
Till you get it locking back just load one round at a time in the magazine.
Are you sure that you have a 308 buffer and recoil spring.