in the pic, it looks like the reason for the gaps is that you are changing colors before you complete the row. you have to slip stitch the last stitch to the first stitch so there are no gaps. i think you are switching colors before you slip stitch the end of the row.
yes! just carry the color up, there's no reason to drag it around, it will be there when you come back around, just pull it up, but not too tight, it needs some slack.