Can I use hot water to reprime my well pump and to try and thaw out the well. The pump and holding tank are in a well pit approx. 3 ft deep

If the ground is frozen to the depth of the pump at the present time, there is danger that the hot water would re-freeze, and you would have an even worse problem. I would wait until the ground has thawed and freezing weather is no longer probable.

Why did the well freeze? Did you leave the well open and allow freezing air into the well?