Please help my dog is scared of everything

Can he see outside form someplace he feels safe. Imagine how you'd feel if some giant just picked you up and carried you someplace you were terrified of. Now imagine you were allowed to sit someplace safe and watch the scary place for a while, then the giant asked if you wanted it to walk out there with you and; promised not to go to too far and, that you could go back when you got nervous.

Better right. Same idea with the dog, little by little. If after a few weeks you can't make progress, it's time to talk to your vet or a behaviorist.

He is likely temperamentally fearful, nothing you have done and difficult to overcome. He needs careful counter conditioning to overcome his issues which may take medication and definitely need an expert behaviorist. This isn't particularly unusual so many have written on the topic. Patricia McConnell's 'The Cautious Canine' would be some help. Dogwise's list on the topic if you'd like to see what sort of thing can help. If you haven't worked much on training dogs a 'project dog' might be a bit much though.

Your dog is likely genetically programmed to be afraid. Did you ever get to see the parents and how they act? How big is this dog?

The very best thing you can do is try to keep things positive and happy and not push or pull. The more opportunity the dog has to go forward on his own, the better. Steps forward should be heavily rewarded with food IF he will take food (and it needs to be the best food like roast beef or something else the dog is a bit crazy over). This is a very incremental process and will take a lot of time.

This type of dog is always going to be limited. Your "job" is to try to make him comfortable in his own skin in the house and outside the house. A dog that submissive pees and also loses control of his bowels is going to be a life long challenge.