i don't know why you would be cutting your yarn, there would be none to knit the following stitches with if you did this, and you would have to reattach the yarn in order to keep going.
You have the jist of it. You cast off the requested number of stitches then just continue knitting with the same yarn.
The decreases are done at each end, yes.
If a little dreaming is dangerous, then the cure is not to dream less, but to dream more... to dream all the time! - Proust
currently recruiting for the war i am waging on time, there will be many casualties, but we will be victorious