If you do replant consider Shenandoah Pear a recent development of the USDA specifically to develop a fire blight resistant pear. Another major benefit of this pear is that it's precocious. It starts producing pears quicker than your average pear. But! I never tasted one. I just planted one this year and also grafted a piece of it to a mature pear tree for faster fruit production.

Shenandoah is only moderately resistant to fire blight whereas Kieffer is rated as highly resistant. If your Kieffer developed that many symptoms, it must have been an unusually bad year for this pathogen!

fwiw, NO pear variety is rated as fully fire blight resistant.

"Am I better off just cutting it down? and re-planting next year? or see what happens?"

I'd trim off as much FB infected twigs, limbs, & branches as possible and see what happens. One of my Bartlett's was heavily infected about 4 years ago and after heavy pruning (including the dark colored bark/branches from the main trunk) it came back a-ok the following years. The last 2 years it gave me a bumper crops galore.Whenever a late frost/freeze kills the early blooms I will remove these dead bloom clusters asap as it seems to be the initial infection point of FB and it spreads rapidly from there down the limbs.

:"Whenever a late frost/freeze kills the early blooms"

This is exactly what happened due to the frosts, which I attributed to blossom blast at the time in early April, but now it seems fire blight has hit. I'll take another look today and make a decision. I hate to cut it down after 4 years of watching it grow.