Noteblocks now attach to slime blocks.
Can confirm. I don't think stems should attach to placed pumpkins, doesn't make sense
Since you appear to be missing a roof, possibly a lightning struck your floor and set it on fire, burning some slabs?
Confirmed, should have been fixed in 1.13.1-pre 1. https://bugs.mojang.com/browse/MC-135945
the direction the door is placed depends where on the block you place it. Placing it on right half block places the hinges on the right and vice versa.
You can just break the boat to get them out. Every mob can enter a boat but can't leave it without breaking it. I don't see a problem here.