1)It is possible to make this without a candy thermometer. In order to do this you will constantly through the simmer process have to do a cold water test. To do this, Fill a glass with cold water. Take a teaspoon of the sugar mixture and pour it into the water. Dump the water and observe the sugar left behind. The closer it gets to the hard-crack stage the harder the sugar will be. In the beginning the sugar will be very soft or you will be able to roll it into a ball. At the hard-crack stage you won't be able to roll the sugar or form it into any different shape than it is already in. Make sure you test throughout those 30 minutes. If it goes beyond the hard-crack stage your toffee will just taste burned.