Had to kill a human merchant and burn his wagon since he was blocking the dwarf caravan. Hopefully, this won't lead to war. I'd hate to have to set the world on fire with out magma pump.
I'm in the same situation as well, a human caravan wagon got stuck in the wagon only entrance-exit. I tried opening up other pathways in the hope that it would recalculate, didn't work, now I'm going to deconstruct part of the floor of that entrance to get it unstuck.
I was creating an archery platform at the second cavern level in preparation for baiting and killing a FB with deadly dust when I accidentially channeled a bit of floor which had a wall under it. I quickly tried to build a fortification on it before the FB attacked, but too late. I mobilized the military while it chased some miners around and apparently the marksdwarves hadn't even gotten their ammo (they had been on inactive because of training problems).
Anyways, the military got there and started pounding away with the crossbows and striking with the swords, meanwhile, during and near the end of the fight, a brave miner had gone down to rescue two of his comrades, although the rescue was in vain, the two miners died from the paralysis effects of the FB dust extract. Lost 4 of my miners, 3 of the marksdwarves and one of the swordsdwarves to the fB, only one of them was actually struck down by the FB, the rest through the paralysis effects of the dust.
Also, it appears that the extract only takes effect when you breathe it in since the extract dust is coating lots of stuff, but the half expected epidemic of paralysis didn't happen.
Meanwhile, the dwarven caravan arrived shortly after the fight and collided with the human caravan who decided to actually leave just then. Attempting to get them unstuck in some way right now and winter has arrived on the calendar. I'm also setting up a lava dumpsite to dump the stuff into in case the wagons break and spill stuff everywhere.