First thing I would advise is to get rid of the tubes. They make taming a nightmare. Dont have anything the hammy can hide in until it has gained confidence and is well on the way to being tame. A cardboard box with the bottom cut out so it can be lifted to reveal the hammy makes a good bed box.
The hammy has had a bad scare with the cat by it all the time. Why did they let it do that
It also sounds like it may have a bit of cage rage where they become very territorial. You need to take it out by herding into a box or ball using something it cannot bite and have a treat in there so it associates it with something nice. Once in take the ham well away from the cage to a low, soft surface and start taming. You may need gloves at first if it is very nippy.
It will take time to undo the fear but with patience and perseverance I'm sure you can do it.
Well done for taking on this little hammy and good luck