Most mainstream Japanese lager is made partially from rice (in these lagers, over 1/3rd of the grain used is rice), so the flavor difference is probably already familiar to many people.
From a cursory search, yes. It is more toxic than ethanol, even in gross terms like LD50.
https://pubchem.ncbi.nlm.nih.gov/compound/isoamylol#section=...
I am not aware of such uses for alcohol, but for hallocinogenic drugs, there exist people who don't use them for hedonistic pleasures, but for getting creative, scientific or spiritual inspirations.