That E1 must be the termistor input. It isn’t labeled on the OP diagram (that I can see) and the parts hanging on it in Marion’s diagram make it look like a good input pin.
I’m not sure what else you’re asking besides the probe question. You want to have a relay for things like the spindle and laser, but you also want to control the laser with PWM? Controlling a relay with a spindle can be any pin (as long as the relay isn’t just a standalone relay). You would only toggle that occasionally. The Laser PWM would probably be better on a fan output pin, so you can toggle it with a mosfet instead of a relay. IIRC, grbl has the concept of a spindle on/off separate from the spindle speed control. So you can probably assign the first to any aux pin, and the second to one of the fans.