Yep, that peanut is probably the clincher- almost certainly your boat. That makes me re-think the whole transom thing. Maybe not a total re-build after all. I don't know about the rear seat, but often either different workers did things a bit differently, build specs changed over time, or available materials dictated a deviation from the norm.
Your boat is an all-wood boat, so it shouldn't have been covered with anything except paint on the exterior and varnish on the interior. You could prime then paint, or paint only. Manufacturers will give you their recommendations, and there have been lots of discussions here about paints and primers.
You should also search these forums for fiberglass removal- many great tips. I think Kathy Klos and/or Denis Kallery (and others have) posted some detailed comments about f/g removal, and Kathy has a video of Denis removing 'glass from a canoe. It may just fall off in one whole piece, which you might choose to use as a bathtub, or it can be adhered well to the hull. If the latter, do check for advice here. Wildly tearing off the fiberglass will surely take chunks of your nice cedar hull with it. Just ask Peter Mueller- he had to pass on what would have been a beautiful canoe because the seller pulled off great sheets of fiberglass to show how easily removed it was. He was right. The 'glass came right off... along with sad little pieces of the hull.