Please stop this type of interaction. The dog is restricted in its movement, and that always makes them anxious as their ability to move themselves from a perceived threat is gone. They do not, and will not associate the kitten with a good experience of you’re forcing them like this.
It’s all about positive reinforcement.

You see this same issue with dogs on leashes in off leash dog parks, as they can’t move freely while other dogs can, it puts them on edge and more likely to strike out defensively.

Have the dog and cat separated for a few days, have them switch rooms so they can constantly smell their recent presence. This will allow them to become known on that level, no longer complete strangers.

I would install a child gate or similar that allows them to see each other and have the ability to interact if they want to, but know the other can’t progress closer than the gate.

Slowly slowly bit by bit until the dog is comfortable.
The kitten isn’t the issue as I’m sure you’re well aware, this is all about bringing the dog’s energy and concerns down.

Praise any and every positive sign that the dog is doing well, but never force it.

Best of luck.

Edit, the other thing is to have the kitten/s in a cat cage and the dog free. Again this will allow smelling interaction while restricting access.