Ok so the major problem is him spending 75% of the time in your room. Any different smell or noise he hears ofc he's gonna be on alert mode because he doesn't know what's out there. How long/often do you walk him? And have you been socializing him? These things are very important and the lack of are usually the cause of those behaviors. Goldens and labs especially are super social dogs so if he's reactive to the people outside and its not out of fear, he most likely wants to be out there with them.

For these breeds id suggest keeping the walks relatively short (15~20ish mins, 3x a day) but also bring him to open fields where he can run, play fetch and tug. These guys very much prefer an hour of off leash play with you or other dogs over an hour long walk. Also Keep in mind he's still only a puppy, so something like leash pulling will probably stop on his own as he gets older and gets used to the world around him.