Having a problem of hard start which is running down the battery

hard start problems on a diesel are most allways a problem with injectors pressure leaking down cummins some modlels dont have starting glowplugs some do , its harder on starter and batterys , till a failure point is reached on one or all of them

Why would anyone remove the pos cable while running. thats how battery gets charged. Hard starting while at op temp? timing retarded to far?

It could be a few things with out having the car here it's hard to say but what I would do it put a isolator switch off the battery so it won't run the battery flat until problem found

You mean it struggles to turn over? If so then it could just be a knackered battery

This engine 'loves' glow plugs! One goes and the others try to handle the amps. Change them and you will have no probs! Other than that, I feel this is about the best diesel truck made!

You need to check if your alternator is charging. Buy a cheap volt meter from Harbor Freight for $3.
The battery should normally have about 12.3 volts.
When you crank the starter, it should drop down to about 10 volts. Once it starts, by jumping, it should go above 12.3, and as high as 13.5 when you rev the engine. If it never goes over 12.3, the batter will never get charges, and will eventually run down. But the alternator should have an automatic 12 month warranty. Take it back to them. And yes, running the windshield wipers will draw more current.

Very likely the new battery is defective - it happens. If you have a know good new battery, then also connect a jumper from the battery negative to the block just to be sure its not a defective or loose ground cable.

check the battery and alternator or connections

Here it is.

I think you are onto something. The thermostat in my opinion is too low causing the radiator to not cool enough before it is sent back into the motor. The block and the pistons are heating up causing it to run poorly. When was the last time you had your radiator flushed? ( I would have said that the headers are heating up the starter and this is causing the drain on the battery but you stated that once you get the car started it runs rough so i would have to rule the starter out.)