Are you saying they built those queen cells during the 14day treatment period? Did you inspect prior to treatment?, as 14 days is not long enough to build a cell and hatch a queen.

"Chewed open queen cells"  Opened on the end or on the side? Open on the end is a hatched queen, open on the side is a dispatched queen. A partial or torn down cell is somewhat normal, they may keep a partial cell ready just in case. The presence of royal jelly would also be telling, a partial cell with jelly would indicate the girls are serious about a new queen.

Is there any open brood in your hive?

Looking at the big picture it probably is too late. If a queen hatched today it would be 30 days before you had any hatching brood, if everything went perfect, mating and all that.

In those 30 days your hive should be building resources to over-winter, if we have a really mild winter there is a possibility of survival.

You need a laying queen right away. Or consider combining with another hive for the winter, that should give you a strong colony for an early spring split, or stack it over a strong colony with a double screen to keep them warm? you have options.