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You need to implement IRecipe#getCraftingResult to iterate through the InventoryCrafting and find the input ItemStack(s) that will determine the output NBT, then create and return the output ItemStack with the appropriate NBT. As Draco said, I do this for item damage in the ShapedArmourUpgradeRecipe class.

Cancelable means that where the event is used, the code queries if the event was actually cancelled before continuing on with the operation. In this case, it isn't cancelable because it's an event informing other code "hey, this happened." It's too late to do anything about it.

You can use the forge multi-layer model with the forge blockstates format, to render parts of the model in different layers. In your block, override Block#canRenderInLayer to return true for every layer which your block has. Then in the blockstates file, define the model as "forge:multi-layer". Add a "custom" tag, and inside that define each of the layers with the model to be rendered. I have an example which uses both translucent and cutout layers for different parts of the model: blockstates, block code.