How should I interpret a book editor not responding to me after accepting my chapter proposal?
Your clock is running faster than their clock. They have a lot of people to coordinate with and a lot of editorial work, I suspect.
This isn't the only publication they are dealing with, most likely. And if everyone is sending them mail every few days it just bogs down the process even further.
It may even be a good thing that it is taking time. A predatory publisher would be after you quite quickly for payments.
Perhaps you should just relax.