Don't over look the starter. I had the same thing on my truck last year (7.3L IDI). No matter how long I charged it, jumped it, or what ever, it just didn't hardly want to turn over. When I went to go to work, the truck turned over a little slower than it had been, and it acted like the batteries drained real quick and then nothing. Started my wife's car, and hooked up the jumpers and let it charge for an hour or so with very little effect. Tried using the 75 am boost along with the car and still it would hardly turn over. After spending $230 on a pair of 1000 cca batteries, I learned my started had died on me. Put a new starter on and with the original batteries, she fired up like she was brand new again. Thankfully, the store took the batteries back the next day
If your solenoid is pulling in, and you are turning over, then adding the booster should have got you started. Since you said that it has electronics, I assume that means that a computer controlls the injection cycle. So if it's not the starter, you could be in for one heck of a time. Diesel only needs fuel, high compression, and a little heat. So if it doesn't start either you're not getting enough fuel, or your not getting enough compression for the temprature that you are running at. The battery and starter will slow the system down and reduce your compression, but all the current in the world won't help if you're not getting atomized fuel into the cylinder.
Just my 2 bits,
Mark