I believe you are using the wrong type of model to solve the problem. The tf.estimator.LinearClassifier() will classify inputs into groups (labels), which is what the error is complaining about. Since you want to compute a number for each input and then compare the predicted and actual numbers, you are going to need to use something like tf.estimator.LinearRegressor() or some other model that calculates values and doesn’t just classify inputs into groups.
I used a keras model of several groups of dense/dropout layers and experimented with the dense size and dropout rate until I was satisfied with the model’s performance, but I am sure there are other and probably better ways. I basically adapted the TF predict fuel efficiency example for the regression model.
Good luck.