I havn't used straw but imagine you would be better off using a propper snake substrate like asphen or the products like repti bark (asphen my prefered choice).
As to heating i keep mine at between 82-86 f for the warm end during the day and 78-82 during the night, with the cool end going with the room temps, which is usually about 74-76 during the day & 70 ish for night time depending on how cold it get's (I live in the sunny UK).