I usually include in my where clause CallDispositionFlag='1' to ensure you are only counting handled calls as from my understanding your TCD query would also count short calls etc

Were you able to box out these two tables? I am going through the same process and find that for every one call in the Half_Hour table there are 3 records in the termination call detail table. I would be very interested in your findings if you were successful.
 
Brandon McDowall