Okay, so I looked at the save and I'm not certain I saw the issue...
The first thing I noticed was that the marksdwarf squad wasn't active. I activated it and one of the two dwarves in it, Fikod, went to town immediately. The other dwarf, Shorad, wouldn't train at all, but I discovered this was because both of them were assigned steel crossbows and there was only one to go around. Changing the assignment to any material crossbow and unforbidding one of the wooden crossbows caused him to equip himself. I went ahead and deleted the rest of his uniform, too, just to speed it up (equipping can take a while, in my experience). Then he began to train as well. A short time later you were down to 50 crossbow bolts, so I set the Craftsdwarf shop to make more bolts. They continued to train for about a season, then I got bored and opened up Hell.
Anyways, what I DID notice was a bug thats been confirmed by several other sources -- once a dwarf uses his one assigned group of bolts the game takes for absolutely ever to assign him a new group of bolts and in the time he spends waiting for the equipment system to catch up to him he'll stand around with Soldier (Cannot follow order) as his job. Eventually the game does catch up and assign him a new set of bolts, he'll run off to grab them and use them all up and return to waiting patiently for the game to catch up to him again. It's crap and it definitely slows marksdwarf training, but doesn't stop it entirely, and as far as I know there isn't any workaround for it except to never use bone bolts -- bone bolts come in stacks of 5 while all others come in stacks of 25. With this bug in, that's a huge difference in time spent actually training.
In other news, another thing I noticed was your fort's absolutely ridiculous FPS. Year three and 100 FPS? Holy crap. I breached all three cavern levels and had two huge migrant waves... and still 100 FPS. I breached Hell and while at first FPS dropped to 10 because all the demons were stuffed into a single tile wide hallway with almost half the settlement also in with them, the steam beasts were spamming their dust attack and every unit in the hallway was smashing itself into the walls several times per frame. That slowed things down something awful. But once they got out of the hallway FPS shot right back up to 100 again.
Trying to figure out why your fort has 100 FPS on year three when I'm usually at 60 FPS by the end of year one... my only real guesses are either your much smaller layer count or the tile set. I'm using Mayday's tile set, but you're obviously using something else. Mayday's tileset seems to not only replace the different colored ASCII characters it also adds many new graphics entries while yours doesn't seem to, or at least not as many new entries. I wonder if that could have an effect? Alternatively, you have a total of only 57 layers from ground level to lowest possible level while my current map has 162... That's almost three times the space, but all of that additional space is just unmined rock -- we both have all the features, all the caverns, the magma sea, Hell underneath it, etc, and the same size embark (I'm guessing; yours looks like a 3x3 like mine is). I thought pathfinding was supposed to be the big drain? We'd have the same amount of pathfinding creatures and the same amount of open space to pathfind over, I just had a lot of extra empty space between features.
So, I guess I'll have to try a fort with a different tile set, and another fort with a much shallower amount of empty rock (assuming you can set that in worldgen parameters?) to see which it is that makes your fort three times faster than mine. Because holy crap, I really want that kind of speed. Playing at sub 10 FPS with an i7 processor is just lame.