Right, alcohol, sugar and salt all change the hardness of the ice cream but you can only add so much until the flavor isn't what you want anymore. I don't think the ice cream texture is due to the melting point, though, that the post talks about, it's also whether large enough ice crystals can form.
It feels like cheating but adding stabilizers (gums, mostly) was really a game changer for our homemade ice cream.
