Welcome to cruise-chat. We don't have a lot of message traffic about Island Cruises, but I can answer some of the questions.
Kettles are specifically mentioned as not being allowed, along with irons. Both are considered fire hazards. BTW - the ship uses 110V U.S. current.
The bar prices are typical of most cruise lines - $2.50 for a can of soda, $3.50 to probably $5 for beer. $4 to $9 for a glass of wine or a cocktail.
Tap water is perfectly safe to drink. I do. It is tested and purified and in many ways safer than bottled water.
I can't imagine any cruise ship not having karaoke these days. I am not positive about it for the Island Escape but would expect to see it.