A lot of flute players play at an angle, but that doesn't mean you shouldn't. If you play with a straight head and flute, people will notice because you stand out and look much better. People like your band teacher. If your hands get tired, rest them in your lap for a little bit. When they feel better, start playing.
Scales are important for a number of reasons.
One reason in because when you memorize those scales, reading music will be easier because you know the key signature from those scales. Another reason is because Band directors look for memorized scales while auditioning for chairs. Especially a lot of octaves. The chromatic scale is the most important of all. The chromatic scale has all the notes on the flute.