If the pressure is fine and the car is that hard to start, we'v got to determine if spark is happening. You can do this by yanking a plug cable off and holding it near the block while cranking, you should get a spark.

If it is, then we must wonder if the injectors are being commanded to open. The only way I know to determine this, is to use an oscilloscope and probe the ECU-side lead of one of the injectors to see of the pulse is there.

Beyond that, I suppose we could look at the throttle body - is it open too far or closed too far such that the fuel/air mixture is way off?

As to the plugs AND injectors, these car's ECU seems to be FUSSY AS HELL about the parameters of their electric supply. That's a techy way of saying it can all be your battery.

If at all possible, substitute another battery. Yes, a battery can be sufficient to engage the starter and turn the engine over, and yet not start the car. I know it sounds like I"m talking foolish, but we've seen this time and again.
In fact, I had a Dodge Durango that did exactly this. We had it towed to a garage and they worked for an hour on it, could not see what was wrong.

Traded batteries between my van and Durango - Durango and van started right up. Swapped them back, Durango would not start.

The ECU/PTCM, what ever you call it, can do some WEIRD stuff because of battery voltage being too low or unstable. And you might read the code(s) to see if there are any pending codes that point to things like "too lean" or "too rich" as this might give you a clue as to what the ECU sees when the engine is running in closed-loop mode. Perhaps things are off enough to make starting hard, but not so far off that, once the engine is running, it prevents the engine from running.