Trying to learn mosfets

It seems stable from what I can see

Not sure what the circuit is supposed to do but the Teravolts are from the 9A current source going through the high impedance of the transistor with no gate voltage. What is it you're trying to do (what output do you want from a specific input).

I mainly want to just learnthe correct way to input transistors to step up my voltage say a 120ac to a high enough dc current to make a small welder without using a big transformer. Like the inverter welders. Im trying to grasp the proper way to input the transistors and the reason for it so I can understand I keep watching videos and I'm just not wrapping my head around it. I love knowledge and love to learn I just don't have anyone to show me so I learn through messing up mostly

To increase the current you'll need to lower the voltage not increase it, but in a way that allows you to draw the same amount of power. Without using a transformer (which directly converts voltage to current) you need to think about where the energy/power is coming from. The only way I know of to get a high current without a transformer would be to store the energy (using capacitors and probably inductors) then draw power from your store at a lower voltage (e.g. using pwm to control a MOSFET and limit the power). If you're look at a spot welder that can be fairly simple as you just charge up a capacitor bank and using a MOSFET or scr dump the power across the weld and wait a second for it to charge back up. If you want a continuous 100-200A supply without a transformer that's going to need a more complicated controller.