I don't think you should continue to walk them either, not because I think they're a "dangerous" animal, but because you could get hurt anyway if that makes sense.
They need training beyond a dog walker. They need someone to work with them regularly, they need more than walks and runs. Walks and runs, in my house, don't do **** to curb energy. Like someone mentioned, it only seems to bring up energy levels overall.
If you lived with the dogs, great, because it's going to be work on everything, not just walks that will make this better. and one dog at a time. It's going to be all the interactions, from when and how you open a crate, to how they are leashed, to how they act when the door is open, to making them chill while i'm watching TV would all be a part of the plan. and that's hard to do, when your'e just showing up to walk them a few times a week.
When I picture this, I don't even see it as a bite. Technically, yes I know it is, but anything that's not a, "I really want to hurt you bite" doesn't count with me
. I can see this as more of him barking and your ear just got in the way, that said, it's something I wouldn't tolerate either. It can happen, but it's not tolerated anymore.
Work has to be done that shows them how to get things, and barking spinning and running out of control aren't ways to make things go faster, which at this point I think that is what they have learned by escalating every situation.
By no means is this a lost cause or even close, I just don't think you'll get it done in the time you're there. It's a much bigger commitment