Hi Nowiegirl
Welcome to Hamster Central
and congrats on the new hammy.
First off - theres no need to be nervous of him! The worst that can happen is he nips you, and even the most determined hamster bite cannot do that much damage. So really try and be calm whilst you're handling him. If he does bite, it's not the end of the world, and you're much bigger than he is
he can't hurt you.
Stroking his head/back whist he's in the cage may not go down well, many hamsters don't like that even when they are tame. It sounds like you're doing well with him, if he's coming to the bars etc. Keep up with that. For handling him, just try and build it up gradually. If you can't pick him up straight from the cage for now (depends what cage you have and how you can access it) using a cup/tube can help. An idea might be to handle him whilst you're sitting on the floor, so if he does jump suddenly he doesn't have far to fall. He won't just sit in your hands, he will want to explore you and his surroundings, so let him crawl over you and run between your hands.
Keep it short for now, even if it's only a few minutes, and build it up gradually.
Good luck
What's his name by the way?