The cavalry is arriving. Gary Sweat, California, and others helped me turn a bucket, milk crate and coffee can of parts into an operating tractor. I'm confident it will turn out ok.
I'm not an expert, or even particularly knowledgeable in this area. But recently I've gathered up a whole pile of these small diesel Japanese tractors, and all have needed work. The good news is that they all work fine now! You'll get it resolved.
I think it's good news that you're getting white puffs of smoke out the exhaust. That means it's trying to run. If it ran when parked, it will run again. The advice Gary gave about checking, very closely, on the fuel filter bowl is good. I've seen that on my tractors. You have to be careful to make sure it's square and sealed correctly. The gaskets and o-rings like to get crooked. It doesn't take much (any) air in the system to make it tough to start. Try re-bleeding again, just to make sure, from filter to injectors.
After that, get either your battery booster or jumper cables. Crank the booster up, or connect it to your car with the engine revving a bit. Really get that thing spinning with the compression release activated, then close the release and let it spin for several revolutions. Try it with the throttle in about the middle of its range to start, but play with it. If the smoke gets heavier as fuel is added (toward you on the throttle) everything is working, and is close to the right specification, at least.
If it won't start after cranking it for 15 seconds or so, don't despair. Go get a hair drier or heat gun. California had a thread around here somewhere that showed how he did it. (Can't find it at the moment) Basically, you want to run hot air into the engine's air intake, and warm up the cylinders and intake manifold. Add a bit of heat, and I'll be surprised if it doesn't fire. It worked like a charm on a little Mitsubishi.
Do yourself a favor and DO NOT spray ether down the gullet. Don't use ether. If you do, the way I was taught was to give the engine "a smell" of it. See how much it takes to be detectable to your nose? That's what you want to give the engine. The quickest possible burst, outside the air filter box, is enough. All you need is a tiny bit of added heat, and that's all it will take. Don't use ether. I'm not condoning or approving it in the least, and the last time I ever got spanked was when I went to use a can of starter fluid on the diesel crawler. I deserved it. :laughing: I was taught that way to use it though, and the stuff we used it on still works. Use the hair drier. If the engine is going to run, that will work.
Pull starting it is a good idea, but I would be almost certain that you'll need, at the least, an implement on the back of the tractor, or some other weights, to get the engine to turn. The gear reduction on these is so much that even in 8th gear (4th gear, high range) when I tried to pull start my girlfriend's YM2000 it would skid before the engine turned.
Gary's tip that it may be some stuck rings bleeding some compression is maybe useful too. Blast some diesel, WD40, or penetrating oil in there, let it sit. Then spin it over a few times with the injectors out to clear the cylinders. It's the right thing to do, but I'm impatient and would probably just borrow a hair drier, masking tape it to the air intake, and then never hear the end of it once she figured out what I was doing....
If you're handy enough to get this far into it I bet you'll get it running soon. Any tractor service place should be able to diagnose and work on it for you. They're really simple and all pretty much the same, based on the Kubotas and Mitsubishis I've looked at or own.
California's point about safety is important, too. A diesel like this needs electricity only to spin the starter motor. If your luck is anything like mine, the first time the tractor will start will be if your hand, head, or other important part of you is somewhere it will get pinched or chopped, as soon as you halfway turn the engine. Shut the fuel lever off, and wire open the compression release before you do anything involving spinning the engine over by hand.