The truck is factory no aftermarket anything. I will check the belt tension, maybe this is the cause of the batteries and altenator all being bad.

 

Unless the truck was ordered with the upgraded 140A alternator the stock one on the truck was 110A and woefully undersized. It doesn't give enough juice to both run the truck and fully charge the batts, so they tend to live a short life. The Alt itself running always at max output also has a shorten life.

Your other (non-main) FICM readings are low, IMO. Lowest I've seen any of mine is 11.5 and that was a blip. (BTW sorry I missed your FICM monitoring earlier). It's still consistent with the glow plugs being on and now that you have a "supposed" 140A alt, you shouldn't be seeing those low numbers.

So you could have an alternator not living up to it's advertised rating (wouldn't surprise me), or you could have an issue with your FICM, or possibly with glow plugs? (someone with more knowledge will have to take on how GPM or glow plugs themselves fail).

So what's your batt voltage during this early start period? Mine sinks to 12s and then come up when GPs kick off, around 13.8V -- it tracks with the FLP/FVP which will drop to 12 but then back up to 12.5V. I do have the factory upgrade 140A alternator and my original batts lasted 6 years (and even then just one got weak).

On edit: strike the Q on your batt voltage, I missed that too -- crap it's not even time for cocktails yet...

 

One other comment, if you have sealed batteries a hydrometer will do you no good.