I would agree with your assessment that the button stance could have stood to be a bit lower - 3 cm would have made a world of difference - but as it stands, the jacket looks fine, and it is a proper length for you, either by the position of your thumb joints to the hem, or to the fact that it (I will posit, since I can't see behind you) covers your rear correctly. A shorter jacket would have looked much worse on you.
As I said in an earlier post, my over all impression was that the jacket looked to be on the short side. After having stared at the photo a little more, I think it's the short "top" (the part above the buttoning point) that causes the odd look. So even if the jacket is of proper length, the top/bottom "balance" (in lack of a better description) is off because of the high buttoning point and messes up the image of the jacket as a whole. But trust me, I have all kinds of sympathies for problems like this as I am tall (as in very tall) and run into these problems all the time when trying OTR suits/SCs.
Keeping my fingers crossed that your MTM works out