I can see from the screenshots you made the same choices as me. Frustrating that it remains 2/3. Its quite a disaster to lose progress to fix a bugged quest, and I can see you take care in your towns layout too. Nice pic, with the kids running in the foreground!
Spent a bit of time looking at the save games, and while there is some text in there (npc/quest/village names etc) most of it is coded, and even then the quest labels are obscure, I couldnt see a pattern.
My thoughts are
1) Try to load an old save prior to that quest just to see if its possible to complete it. If you can bear the pain of replaying back from that point (ie before the quest bugged), then thats one way to solve it. Painful I know :-(
2) Random thought: Maybe if a season completes while the quest is in progress it causes the bug?
3) Try asking on the steam forums - the devs are present there - maybe they could take your save file and fix it up for you?!?
4) Unless something changes, so far the game is not exactly quest dependant, so for now just play and enjoy. The most significant element of the quest chain (so far) was getting upgraded to 'town' and the increased building limit, and you get that from the main quest chain, not the 'story quests'.
For me - at some point as the game nears or leaves the development stage, I will be restarting my village anyway. e.g. some of my orchards are too far from the barn and its not easy to change my village config to cope with such game changes, so in many ways I am now seeing my village as a 'test site' anyway. Plus I am eager to build in another location.
So if you are of the same mind you will be restarting the game after it leaves development anyway, and then you can have another stab at this quest chain.
Wish I could be more helpful but its all I could think of. Good luck with your choices - think of the children! Heheheh.