The solution to your magic wand problem is actually a staff and flowing robes... I love when one dumb trope is the right solution to another. Much
First the Staff:
Much like your chopsticks proposal, you are using a device to hold it away from you. The staff puts distance between your hand and the wand which is important when you dealing with limited insulating materials. While the heat of the wand is enough to cause 3rd degree burns, the head of the staff will heat up a lot at the end but much much less at the handle; so, slip the wand into the end of a staff and it's like holding a pot over a flame.
Your Wizardly Robes:
Ever notice how people who live in deserts seem to like to wear over-sized, full body clothing? The reason is because air is a great insulator. By wearing lose fitting wizardly robes your robe will heat up from the blast of heat, but poor contact between this surface and you skin means that it will not transfer that heat too you. Most robes will be made out of wool because it is the most fireproof natural fiber, but asbestos cloth is also an option in your 13th century setting for those wizards willing to trade good health for more powerful spell casting potential.
He could also use a cloak held out in front of his body to shield himself from especially powerful heat blasts. To keep his hand safe while doing this he could drape your cloak over the staff rather than holding the cloak directly.
To fully protect your body, a well to do wizard would also cover his face with a conical hat or hood (because it minimizes heat and maximizes coverage), a scarf, and some manner of goggles (yes, eyeglasses existed in the 13th century so goggles are a distinct possibility).
The Castle Problem: