I am running it on a MBP too, same OS. This is how I got it working. I merged the old and the new game. For this, you have to open the contents of the game and add Ch7 and CH7 manifest to the old chapters file. Then you overwrite the contents file entitely. That's how it worked for me, although it is not 100% bug free. Possibly I did not have the latest version of Ch 6 part 1. IIRC there have been some bug fixes on that one, and I may have missed those. I don't want to change anything now, however, because it cost me quite some time to get to this point and I don't want to loose anything.
It is certainly playable and enjoyable. The most annoying bug in my case is that I get black screens, i.e. only text and hotspots but no pictures, when using the scroll back or scroll forward arrows. Not in all cases, to make it more difficult to understand.
Another slightly annoying thing is that the stats suggest that I scored 100% in all the previous scenes, while I am certain this is not the case. I replayed some of them and was able to find new content. Which is nice, but I would rather know if there is something new to find or not.