Hey there with the BG and layer 3. For layer 3, I had to correct palettes and 1 tile and has to fight a bit more with layer 2, but did it. Here's what you can do:
-you can view the sample level to see how both the BG and layer 3 are set up.
-the palette for layer 2 is organized. It uses palettes 3 and 5. Both should be easy to edit.
-you can set layer 2 to an appropiate size.
-BG has 276 8x8 tiles, meaning it overwrites BG1, BG2 and FG2. Only bushes are removed.
-BG uses 181 Map16 tiles.
-layer 3 uses 5 palettes, leaving the original colors safe.
-Still, you should use the DKCR Sprite Status Bar or the Minimalist Status Bar.
-layer 3 uses 381 8x8 tiles, making this a big layer 3 tile consumer.
-Both layer 2 and layer 3 have their own files required to insert.