Well, I checked the MIP website and they're not in there specifically for the BD, maybe one for another brand fits?? No idea about it.
Not the pin from the axle into the spool, the other side, into the shaft (well, roughly translated from dutch: from the cross coupling...). Never seen that before but it happened to me, and no yokomo ordering number on it.
You're right about the spool, but then its still strange that for you its the other way around. You wear the diff halves earlier than the spool.
Do you also drive rubber on asphalt like me??