Yes, I agree that ICP psi has to be a MINIMUM of 500 psi for the injectors to fire. I would be concerned as why P0611 set as well though. That code only sets if the PCM detects FICM_M voltage go less than 45 volts at some point. It may test fine for now, but check it again while it's under load (engine cranking over, or under heavy throttle if the engine runs) and see what kind of voltage readings you are getting.
But first and foremost, you'll need to address why you're only getting 18 psi of ICP pressure. My advice is to let the engine cool down to see if it starts. If it fails to start due to low ICP psi PERIOD (while the engine is hot or cold), the very first thing I'd do is pull the IPR valve for a look/see. If the screen is missing/sucked in/damaged, replace it!!!
Once you address your low ICP issue, you will need to look further into why P0611 set, or you will be left on the side of the road again, without fail.