
I don't have a lot of experience with travel sickness and dogs -most grow out of it. My oldest Papillon hates travelling by car and whines, but this goes all the way back to when he was a tiny pup and had seriously injured his eye and had to be rushed to the vet in great pain -he now puts every car journey together with that. Hopefully somebody else will have advice here.
But as for the having a go at different dogs etc, I've just been through this. I got a 9 month old Papillon bitch last summer who had not been socialised and she was terrified of bigger dogs, and her way of dealing with it was to attack first. In other words, she would rush at and bite any big dog she could get near, always bite their back or bum and then quickly run off. She had my MIL's Labrador absolutely terrified of her! We asked the trainer I train for to come and do a home visit, and she told us we must get her used to gradually being around bigger dogs without anything happening to her. Teach her there is no need to be scared. So we started by having her on a lead and just sitting on a chair close to another dog -but it had to be another dog that would largely ignore her. Gradually over time got closer and closer (this took weeks). She was rewarded with praise and treats when she ignored the other dog, if she barked she was ignored. Taking her to training classes at this point was impossible as she would attack anything in sight and would not keep quiet. After hard work she can now go to training club and be in the same hall as lots of other dogs, she doesn't bark, she doesn't try to bite, and if she gets worried by a bigger dog and tries to run off, I ALLOW her to hide behind my legs (rather than forcing her to confront), so she learns that nothing is going to happen to her. She is getting better for each week and is like a different dog.
The key is really to do it all slowly, so try to stay a a distance from everything at first, be it dogs or bikes or whatever. Reward when he sees whatever it is without doing anything, ignore when he barks. It does work, but it does take a lot of patience.