The thyroid is a gland which produces hormones. Low thyroid would mean that your thyroid is not functioning as it should. There are a few medicines that you can take to correct the situation.

Yes. Acupuncturists can treat low thyroid levels.

There is Hypothyroidism- low amounts thyroid hormone, and Hyperthyroidism- high amounts of thyroid hormone

The question can't be answered unless you say what drug you're on and what thyroid test is low.

There are many causes of dry eye and thyroid function is one of them so if the thyroid production is low it can be an important factor and replacing the thyroid hormone with pills can improve the dry eyes in some cases.