New to 3d printing, need help, please

Hi, I built a classic Rostock about a month ago. I bought almost everything online except the wooden parts which I made. I am having problems with making it run correctly. I can make it move only slightly before it stops. Pressing any of the home keys (if it is within about 10 mm of the top) sends all the carriages to hit their respective endstops, light the red light then bounce off of it a couple of millimeters. It sounds like it is hitting the stops pretty hard, but that much seems to work. I did something yesterday that sent the end effector continuously downward in a smooth motion hitting the glass before I could stop it, I then changed the direction, and it is back to not moving more than about 10 mm.

I am using Pronterface, if I send an M119 to the printer, it says;
X_MAX TRIGGERED
Y_MAX TRIGGERED
Z_MAX TRIGGERED

It also says:
echo: endstops hit X:588.55 Y:631.20 Z:645.90.
These locations are impossible, aren't they? The max height is only about 400 mm.

It is a classic Rostock, GT2 pulleys with 20 teeth, geared extruder, 12 volt 30 amp power supply, 20x4 LCD display, Ramps 1.4, J-head, mechanical endstops with boards. I am using Marlin, which I got from Github, the delta version. I am using 1/16 microstepping.

How do I turn the trim pots down? There isn't any mark that tells me where it is now. How do I reset the counter to tell the printer its location at the home position? I feel encouraged that it moves at all, but I really want to try printing, and I feel it is close to doing that if I could only cure the small problems.

Thanks for reading this.