I finished it!
And it fits him perfectly. It looks great; I'm so happy. The zipper was a bit more challenging than expected, but it's done. I machine sewed it to the vest and then hand sewed the ends with extra care. [The zipper came from Zippersource, a great place to order custom zippers!] For more info. on the project you can check ravelry or here.
The pattern is from an Australian knitting publication - which I borrowed from a friend - and the yarn is an undyed, locally-spun worsted weight wool. I learned a new cast-on technique and how to machine sew in a zipper. Overall a great project, but the challenge to finish was tough. It took under 750 yds. of yarn to knit, which made it an budget-friendly project too, but the zipper was an added expense.
If I were to knit the pattern again I would do an applied i-cord around the armholes as the Italian cast-off is difficult to manage and, I think, unnecessary there. The i-cord would give a nice finished look and match the detailing on either side of the zipper. I would also probably shave a few centimeters off the length of the neck/collar. It's pretty long.