@Canonfodder - Bristlecone are notorious for being difficult to grow in climates away from their native habitats. Broomfield CO is a suburb of Denver, so you are somewhere near 5000 foot elevation. That's good. Bristlecone do not adapt well to low elevation climates, at least you are within 4000 feet of its native elevation. They are only common above 9000 feet.
I believe you may need to water somewhat more often than the woman at the nursery implied, but you should indeed allow the tree to get dry for a day or two between watering.
If that tree were in my backyard, my first and only task for this year would be to repot to a shallow, wide training container. It should hold at least as much media as the original. Either a home made wooden training box or perhaps a cut down plastic 55 gallon drum or a large nursery pot cut down. The width should be at least 20 or more inches in diameter. The depth should be not much more than 5 inches.
When you repot, do not remove roots if you can help it. Tease them out, arrange them in a wide radial pattern. Long roots fold under the root mass. Then anchor, or tie down the tree into the pot so that there is no "wiggle". You want the tree solidly tied into the training pot.
The media you use should be mostly pumice based. Sift to remove fines. You want a mix that is open, with good air void. Add about 2 tablespoons (roughly 30 mil by volume, roughly a shot glass full) of crushed oyster shell or pelletized horticultural lime per gallon volume of potting media. Bristlecone come from dolomite derived "soils" though the soil is more rocky scree than "dirt". Where there is no limestone, limber pine dominates. Where you have limestone at high elevation, you get bristlecone.
When flattening out the root system, do not remove all the nursery soil. It is okay if some of the old nursery media (usually composted bark) will adhere to the roots. It is okay to leave that. Just work the pumice based mix you use in to fill the voids created by flattening out the roots.
Set the new training pot on slats, rocks or a bench to allow air to get under the pot. This will help keep the lower part of the root ball well aerated.
Build a brace, scaffold or some structure to prevent the tree from being toppled over again in the high winds you get in Colorado. Even a "tomato cage" might work.
Good luck.
