I've not follwed the whole thread, but I'm assuming you're using an installer...
You should be able to slide the balancer on part way. Enough so you can line up the keyway with the key. You don't want to bump the key enough that it falls out of the crank. It's just a slight interference fit that holds it in.
Once you have it on the crank, you SHOULD be abke to put the (factory) washer that goes behind the (factory) bolt over the hole, thread in the bolt from the installer to the crank, then put on the thrust bearing from the installer and then the nut from the installer.
Personally, I just used the bolt and washer to pull it on the rest of the way.
I know it's not the recommended way, but.....
Put a little glob of RTV on the balancer where the keyway is, as oil CAN make its way past. I also rtv'd the back of the washer....
Dennis