I don't think you screwed anything up - this is the standard 1 queue version of Huffman coding. It meets the stated goals of my objective.
Let me try and give some more insight into this fuzzy idea I have. Huffman coding gives ideal compression when the symbol set it is coding for and the frequencies those symbols appear is known up front. Typically, those symbols are single characters and for my purposes that will be true. If the bit sequence '01101' is used but '01100' is empty/unused, I see that as an opportunity to fill in the tree with some unknown symbols. Since all the single character symbols are known and populated, I would plug these "holes" with symbols representing character tuples.
I then realized that I should reduce the frequency of the single character symbols that were part of the newly inserted tuple because not all of them would be encoded. This could then generate a different looking tree with different holes to fill. Looks like an infinite recursion problem.
I then thought - if I can come up with a strategy to populate a tree given a desired outcome, I could just jump to the answer. In my sleep deprived state, I thought the Animals problem I posted got me there but it really just got me back to the beginning.
Cheers - L~R
In reply to Re^4: Challenge: Optimal Animals/Pangolins Strategy