Is it possible to OVER-insure my home?

Yes. If you think your home is over-insured, ask your agent or insurer when they last made a replacement cost calculation specific to your home. These are done by insurers to figure out what it would cost if they had to rebuild your home after a major covered loss. (Like your home burning down.) If the information used in the calculation is wrong, you can end up with an insured value that's too low or too high.

Your tax assessment value, by the way, is not the value used for insurance purposes. The insurer needs to use a value that reflects an actual and realistic rebuild cost.

Also, your home insurance policy should not have the value of the land included as part of the dwelling coverage. Land is not considered to be insurable property on a home policy.