Complex sentence: Portraying a recurring character, David Nykl is not under contract and neither knows his number of episodes nor his character's story arc in advance, although he has appeared in approximately half of each season's episodes.
Split into simpler sentences: Portraying a recurring character, David Nykl was not under contract and neither knew his number of episodes nor his character's story arc in advance. Nevertheless, he appeared in approximately half of each season's episodes.