1. Increasing every 9 st would be good.
2. M1 is good because it's invisible
3. You will not be able to knit the entire hat on circs. You will get to the point when there are too few stitches to fit around the needle. You'll need dpns or something like magic loop or using two circs.
4. dpns look harder than they are, it's a good technique to learn.
5. ?? What have you got to lose? You should learn this sometime, why not now?
6. You'll need to go down a needle size to get the correct gauge. however, circular gauge differs from knitting flat gauge. You might want to try a circ swatch.
Don't be nervous--its a hat, not brain surgery!