Distancia does allow combining accouts for redemption BUT they say both parties must be at a TACA ticket office to do it. So if you are in Seattle and friend in Omaha - not much chance of happening. On other hand, rules vary depending on who you talk to and on which day.
Yes, if you have Distancia miles, they may expire end of DEC -- best to check. If you cannot get a TACA trip beforehand, better get a trip for 05.