Hi there Marina
Halti's aren't a dogs best friend for a while so what he is doing is completely normal. I do have a few ideas to help with the halti.
Try leaving it around his food bowl and bed when you are there. The more he sees it in good situations the better associations he will have with it.
When you do put it on him don't put a lead on him at the same time. Let him get his frustration out for a bit before you put the lead on.
But most importantly don't give up, just like putting a saddle on a horse for the first time it can be very frustrating. but trust me the benefits are huge.
Now for the fear of things.
I think the best thing is to start socialising him at home where he feels safe and under control.
Get friends, semi-strangers and other dogs to come over, but one at a time. get Harry to sit. have them a few metres apart and slowly get him to walk closer and closer.
When he is being fearful completely ignore him. Don't look, touch or speak to him. But the second he starts to show that confidence praise him as much as you can. The more good associations he has with other people etc the better. He can keep advancing as long as he is being confident.
Try a number of sessions with different people etc before venturing out.
When you are on a walk follow the same principles, praise confidence and ignore fear. When some one approaches make him sit and wait for them to come close. Start with a quiet area and as he gets more confident try dog parks the beach etc.
take it slowly and give him time to build his confidence up. Remind people greeting him to be quiet and don't rush him. Let him come to them.
Another thing that may help is some rescue remedy or sedapet before you take him on a walk. This will take the edge off and make him much more receptive to strangers.
Good luck and let me know if i can help anymore
Todd