Wow, a haiku virgin! Buson is certainly a good place to start, especially for you as a painter. He was a pivotal figure in the history of haiku, not least because he elevated Basho to his current preeminent status as the originator of serious haiku composition (haiku-writing had been something of a parlor game in the 17th century when Basho was active), and also because he invented the genre of haiga, or illustrated haiku. You can get a sense of the range of his artwork — Chinese-style paintings as well as the more comic-book-like haiga — with a Google image search.
I liked that haiku too — in fact, my original title for the post was “Peony hellmouth: haiku of Yosa Buson.” You’re right, it is the kind of transition one would expect in an art film. And the poet may indeed have intended the kind of defanging conversion of harm into beauty you suggest. Harold Henderson’s commentary says that interpretors are divided about whether this is a religious poem, or simply one that uses religious imagery. I think Buson meant it to work either way.