Chakotay's Fear Period

Dog training friends, I am in need of some help.  Chakotay is going through one of the "dreaded teenage phases" ( I try to say that jokingly ) of puppydom.  Better known as a fear impact period.  He's at the 7 month mark, so I understand this is normal and I was expecting it might happen ( even though ironically it never really did with Journey ).  Poor Chakotay has gone from being a confident (but sensitive) sassy pup to having weird reactions to situations, people, objects, and sounds he has always been exposed to or has experienced before and been okay with.

His body language is reserved, he won't take treats/toy rewards like normal, and has avoidance or distancing behavior, so I know he is uncomfortable. People he has known since I got him, he acts suspicious of them and reserved to approach for pets where in the past he'd go right to them for love.  With strangers the behavior is obviously worse with over vigilance and general weariness and wanting to avoid contact.

Same thing with certain environmental stimuli; places we have frequented, smells or sounds he is familiar with, he acts overly surprised, worried, or wants nothing to do with it. It has been hard for me to keep his attention and keep him under his threshold of tolerance because it has varied so much from one point to the next.

I know this is normal behavior during fear periods in adolescent dogs.  My concern is if I cannot help him overcome this, it will disqualify him for being a service dog.

Service dogs need to be friendly toward and accepting of all people and animals they meet, for obvious reasons.  If Chakotay continues to show lack of confidence in public and around strangers, it means he isn't a good fit for the job, and it would be wrong of me to force him to do something he cannot, same as it was with Journey having to be washed for medical reasons.

So for all my canine behavior savvy friends out there, any recommended reading materials or feedback you can offer?  I know the general rules just as it is for the initial puppy fear stages in the 6-12 week or so fear periods and any others. Counter conditioning and desensitizing, make everything as happy and fun and AMAZINGLY positive as possible, do my best to show him it's all normal and nothing to be afraid of, so on and so forth. I plan to continue to socialize him to get the exposure but trying to do so without overwhelming him.  But if he won't take offered rewards/treats for reacting correctly or as part of the OMG AMAZING situation pairing approach, is there anything else I can do to help get the message through to him besides letting him approach as he is comfortable doing so?  Depending on circumstance, he may not want to at all on his own, so I don't want to inadvertently reinforce fear with my own reactions or lack of reactions.

I'm not sure how long I should give him to overcome it.  I know normally you'd just let the dog get comfortable with something at their own pace and work on anything that can boost confidence with that object or situation and confidence in general, which I have already been doing. But I am concerned that as a service dog in training he needs more exposure time than a pet dog would to keep him on track and avoid any huge training setbacks.  It is also a matter of how much time till it passes. I know on average it can be several weeks worth.  But if it lasts past that point, does it mean it may simply just be part of his behavior ( genetically influenced or otherwise ) and accept that he probably isn't cut out for service dog work and go ahead and wash him?

That's not even touching on the other possible problem I may be facing with him; I'm not sure if Chakotay is actually going to be nearly as big as Journey was. He hasn't grown as much as Journey had by this point and his paws are smaller.  I am hoping the fear period is directly related to a developmental growth spurt or something and he is about to supersize himself.

Journey for all intents and purposes was pretty bulletproof from day one, and not much ever really phased him - which was amazing considering how bad some GSD can get.  That's why I am more concerned about Chakotay. From the first day I got him, I already knew he was a lot more sensitive to certain things in ways Journey never was.  Journey just didn't care.  But Chakotay does, and the fear period is amplifying it.  I just want to make sure I do what is best for him.  Even if it means facing a similar situation like I did with Journey.