If I'm not mistaken, the undercarriage on that machine looks in good shape so that's one reason to retrieve it. I think I'd go out there again with the tools/parts knowing what you know now and get the pony going, and get the main clutch freed up and see if the main engine will turn. If it's in gear, you won't bar the main engine over although it would move a little I'd think. If it doesn't turn, you can always borescope it and see what's in the cylinders, and then fill them with a concoction of diesel, oil, and whatever else you'd like to dump in there, and put extra protection on the main exhaust. Where did you use your bar to try to turn the main engine?
If you decide to trailer it home, you'd probably want a heavy wrecker like you say in addition to the lowboy and plenty of snatch blocks, and a chainsaw to cut up some logs for rollers. Use the wrecker to lift each end and get the logs under there before dragging it on to the trailer. You could even make that the next trip instead of dicking with the engines