I'll also throw in my two cents worth and say it's never too late to go join a club and get some help.
We have an elderly man at our club joined with his 3yo GSD, who has a combination of excitement and aggression, it's just so overwhelmed by all the other dogs it doesn't know if it should be friends with them or bite them.
The man is going well to hold on to the dog.
But after about a year of being with the club the dog is now able to walk onto the grounds, with his owners shoulder still in it's socket. Join in a class without driving the other members mad with it's barking.
It did take some one on one help. An extra instructor was assigned to the class so that the main instructor's time wasn't taken up by this dog alone.
There are lots of good clubs out there and lots of dedicated instructors, sometimes it takes a few weeks for the good one to surface and show an interest in the hard cases, but generally someone steps up.
I'm sure Trooper is no where as a handful as this dog was. I'm sure with your dedication he will also come along in leaps and bounds.
I think the BC is a great dog for you work on as you can walk past on a regular basis and practice holding Trooper's focus, especially if the BC likes to come to the end of the driveway and check you out. And is non reactive in return.
Stride past at a swift pace as though nothing has happened, talk to him, have your food ready, slowly get closer the the BC. This may take some weeks.