well, regarding this tryptophan idea...

I know it seems intuitive that adding it to the substrate may be a good idea,

but in all actuality, the mushrooms are genetically predisposed to make most of their own

tryptophan from indole and serine, similar to plants. so either supplementing with indole or tryptamine, an immediate product of tryptophan metabolism (getting to tryptamine from tryptophan is what requires a lot of energy, so supplementing with tryptophan is actually counterproductive) would be more effective in theory.