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Their are hundreds of varieties of Penstemon, and the growing zone and hardiness depends on the variety.
It may be too cold for the particular variety that you have planted.

Too cold or too warm and Penstemon will act as an annual.

https://www.gardeningknowhow.com/ornamental/flowers/penstemon/penstemon-beard-tongue.htm

The ASPCA has a website with a directory of plants poisonous to pets: https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/pet-care/animal-poison-control/toxic-and-non-toxic-plants

I assume you've talked to your vet, the person who will have the most up-to-date info. I was able to find this reference: http://www.wildflower.org/expert/show.php?id=12470

It certainly isn't among the most toxic plants listed for cats but it isn't listed as safe either. (https://www.aspca.org/pet-care/animal-poison-control/cats-plant-list). That probably means there just isn't any information either way. I've grown penstemon for years and I've never seen my feline show any interest in it. It is always best to check with your local vet.

Check the soil, is should be evenly moist. Do not let the roots dry out or sit in soggy soil.
Make sure the container has drainage.

In temperatures over 85 degrees F you may need to water twice a day.

Yes, deadheading the spent flowers will help encourage more flowering.

Penstemon grow in full sun; 6 plus hours of sunlight.

https://www.gardeningknowhow.com/ornamental/flowers/penstemon/penstemon-beard-tongue.htm