> I'm glad to hear that the recorder is the flute of the gods
You are entitled to see it that way, but the author thought of his book as a flute heaven owned by gods, and recorders (blokfluyten) as being a subspecies of fluyten. Modern spelling: (blok)fluiten.

> Why is there an apostrophe in front of tweede?
Probably not a typo, rather a spelling error, comparable to English confusing "its" with "it's". In 1644 a publisher was not required to be an expert in linguistic consequence, let alone in standard spelling which was scarcely defined anyway.

A MIDI won't help us with "Bl.". I am not convinced of "Bladzijde". I thought of "bladeren", which might have meant "turn over" (like German blättern), but I am not sure either.

Good luck with your blokfluit and with the church garden.