What is the ruling on a son working in a shop that sells vanilla containing 35% alcohol, knowing that the shop owner is aware of this, and the son may be forced to sell it to a Muslim or a non-Muslim?

If the alcohol added to vanilla remains in its original intoxicating state when added, then it is impermissible to use or sell it, due to its impurity. It is forbidden for your son to directly sell it. He can remain in his job if it does not compel him to sell forbidden items. However, it is preferable for him to seek employment free from doubts. What is definitively established as forbidden to sell, cannot be sold even to a non-Muslim.

However, if the added alcohol has transformed into another non-intoxicating substance before it was added, then there is no impediment to its use or sale.