It's done! What a fun project - perfect TV knitting and I'm really happy how it turned out! :)
I made a few modifications: I used a smaller needle (4 mm), I worked only single yarn over stitches and also kept the stitch between the yarn overs in Stockinette Stitch (i.e. knitted it on all RS rows, purled it on all WS rows) to match the decrease line.
In section 6 and 10 I added my colour B as per the pattern before the update. I weighed my colour B after section 4 and already knew that I wouldn't have enough left for the second half and since I need to use my extra skein, the few rows in section 6 didn't get me into any trouble. And I really think it is a sweet touch and somehow links the different colours used.
I needed 168 g of colour A (Whales Road), 113 g of B (Reflecting Pool) and 82 g of C (Borajas).