You seriously need to have those batteries LOAD TESTED separately, before testing the FICM. If they fail replace them with the proper batteries.
It means absolutely nothing to check the FICM without testing the batteries first. The way these things are wired, you might think that since it turns over rapidly that the batteries are fine, but that is not necessarily the case. The batteries can be junk and still turn the truck over, but not have enough juice to fire the injectors. Keep cranking it like this and risk damaging other components. Load testing is VITAL.
After load testing, but before rechecking the FICM, remove the FICM from the truck. Check all the pins to make sure they are straight in line and not bent out of place or corroded.
Plug each plug in and make 100% certain that the plugs are seated properly. If the plug is off just a hair, that will cause a problem. Both locks need to click on each plug. It isn't always as easy as it sounds.
Once you have done those few things, then check your FICM voltage readings with key on, engine off and cranking.
Next would be to order this from Tousley Ford
. It not only has the parts needed to fix your leak, it also has the parts to replace the weak stock fuel pressure regulator spring. There is an awesome write-up thread on here that would help you install it. Its rather easy and will cure your leak and save your injectors from low fuel pressure.