I think the older Pom x doesn't like or understand the energy of the pup. Not all dogs like puppies. He is overwhelmed and doesn't feel you protecting him from the pup so he is out of sorts. He isn't comfortable in his own home right now.
I would show the older dog that you have his back and you are willing to teach the pup how to be gentle, and to leave the older dog alone when it is appropriate. I would do a lot of obedience with both of them. The pup needs to learn and the older dog needs to feel valued and connected. Walking them together is great but obviously not a good answer right now. But you can certainly have them on leashes in the house and walk around with them. It is also a good opportunity to show the older dog that you are in control of the pup. So if the pup starts to go after the older dog (even in play) you are ready to stop him.
New relationships can take time and usually do work out for the best. Try not to let the older dog escape quite so much, he needs to learn to face the music and experience the pup - if he is always avoiding then this will take much longer.
You might try feeding him in his crate for a while until things settle down.
Love Them & Lead Them,
~Elizabeth & Doug
Dog Training the Way Nature Intended