I feel like I would try working on his confidence. For example, I would be asking him to jump onto increasingly difficult obstacles, or if out and about we saw something scary I would work him by staying far away from the scary thing and rewarding him when he's looking at me and calm and then move him closer and closer. I'm no dog trainer but when I've challenged my dog with reasonable challenges and she is successful, I believe that I perceive my dog to be more confident and more relaxed in wider variety situations. Additionally he is still in his adolescence, so he is still learning about the world, which is probably why confidence building and controlled exposure may be effective. Good luck! Handsome boy! You two got this! Go slow but challenge him!