These things are built by humans one at a time on a semi automated assembly line, aka moved from work station to work station. Most people compare RV manufacturing to cars, which is not the case. Cars are almost completely made by robots, with high precision repetition, with a few people doing a few tasks that humans can do better than robots.
Sawdust, when we bought ours I did not see any sawdust during our PDI. When we got home and starting going through it. We found sawdust all over the place. We planned to clean the HTT really good anyways before using it. So we vacuumed and scrubbed everything down. For the next few trips sawdust kept showing up in the same places. After a few trips and cleanings, the sawdust is all clean and gone. I even had to remove the cover for the skylight in the bathroom to remove sawdust from there.
I know about the furnace and oven and asked our dealer about it during our PDI, and they said they fired them up and burnt off the manufacturing oils. I still fired them up at home and yes they had been burnt off. Even a new furnace and stove for your house has the same exact issue, you just have a larger area for the small and fumes to dissipate over
The water leaks can be a pain. I still check our unit for water leaks even today.
Hopefully you are through the worst of your problems, and you can enjoy the unit more and more, especially once you’re not living in it and get to enjoy using it for recreation with the family.