Help! Turkey done way too soon!

It is possible for the following reasons: oven temp higher than you thought; if you cook the turkey covered; if the oven is small. Hopefully it's not a faulty thermometer. You can also check by grabbing on the end of the drumstick and see if the leg/thigh joint is loose. If it is, then it really is done.

The targets after resting are 165° F for breast and 175° F for the thigh, so judging by this temp your bird is definitely done. Just tent the turkey with aluminum foil and let it rest. That was fast for such a big bird—I envy your oven!