Yes, that was the cliffhanger ending of chapter 5, the start of the ending chapter is about Myriam escaping their clutches as the last ordeal/gauntlet of the game for her.
The game started with them and the game is ending with them (I mean as an ordeal/conflict), this part of the game was planned from the get go when I presented the game, though at first I had planned to go with a full chapter around it, with more intricacies with the family (like the famous Ma, only mentioned here), but I felt that it would only slipped too long into "torture porn" and in the end I preferred to avoid it and shorten up the part to the essential.
Not sure, no, I think you can explore a lot around it, as I answered someone else, it's all about the writing and character, though of course you escape the interpretation of the player that can be far different that what you intended, but that's the prerogative of the player.
On the subject of finishing the game, yes, it was important for me to finish it, as much for myself than for my supporters, proving that I can bring a project to its conclusion. I stated that I would only work on the next project after Project Myriam, but I fear that it might leave me after this with a big hole between the two, so as I exposed my future planning recently, I think I will bring Project Myriam to the main branching point for the endings (which should be next update), then start working on the next project in parallel of working on the ending updates for Project Myriam, so that I can cut a bit on the latency between the two, but I won't be sharing any version of the next project before fully ending Project Myriam though.