tire pressure light and gas-line antifreeze

I am away from home for 6 months and away from my brand new Prius! I have asked my husband to take it for a drive every once in a while. He tells me today he took it out and the car "was not working well". Weather has been quite cold dowm home so he says he stopped at a gas station and bought one of those bottles of gas-line antifreeze and poured it in the gas tank. He also filled the gas tank. He says it is working fine now. Is this gas-line antifreeze stuff safe to put in a hybrid?

Other question, he also says there is a light in my dash on that looks like this: (!) He says he checked the book and it's the tire pressure sensor. He tells me the book says if this light is blinking, tire pressure is low but if the light is not blinking (just on) you need to bring the car for service. he tells me the light is on but not blinking but given the cold temprature, I imagine tire pressure has dropped and all we would need to do is check tire pressure and reset the light with the little button under stearing wheel, right???