I certainly wouldn't risk taking out the end so I could cast off. I suppose it could be done, but it's not easy to take out a cast-on. You can't just pick it out and pick up the stitches the way you could a cast-off. It would require picking up a row of stitches before you took off the cast-on, cutting off the cast on and then knitting the other way. There might be a better way, but I don't know what it is. I say save it for next time. The ends don't have to be exact. It's a hand made scarf, let it revel in it's lack of machine-made perfection.
As for the twisted stitches, I haven't watched the video so I don't know what twisted stitches you're referring to. To knit into the back, however, you just knit into the back loop.
When a 'regular' stitch is on the needle, the front 'leg' is a little bit forward of the back 'leg'. When it's twisted it's as if you took the stitch and reversed it. It feels a little tighter to knit into. If you don't want to knit into the back, you can take it off and put it back on your left needle the other way and then knit it.
I had to laugh when you said you hoped I read your post! Please don't raise me to cult status--I just avoid my responsibilities by hanging around here a lot--I certainly don't know it all!