Laura with your level of inexperience and this dog you can still do Working Trials however I would strongly advise you NOT to attempt PD.
The difference between Working Trials and Schutzhund is that Protection work is not mandatory in the former but is part and parcel of the latter.
Tracking, obedience and agility is not a problem for any dog of any temperament.
A defensive dog is not what is needed in protection work as it should all be prey and by the sound of your post, your dog, for whatever reason) is not relaxed around strangers……….
There is no reason you should not train your dog to do anything (bar protection work) once you have sufficient control over him.
Sounds like you are now on the right track.