You're right. Indeed the motherboard of the 140/145/170 series has another socket for the daughter card than other PB100 models.
It has been a while since I opened a Powerbook 100 series.
As for the plastic standoffs braking off: that's regrettably perfectly normal. They brake due to aging plastics or bumbing the laptop.
It's next to impossible to buy a used powerbook with no broken standoffs on the bottom place or the display backplate.
A few years ago I had an opportunity to buy a bunch of Apple service parts for these powerbooks, mostly bottom plates and some display housings so my powerbooks are in mint condition as I replaced the housing on all of them.
As for the hinges: in order to relief the stress on the standoffs in the display backplate, I can recommand to take the metal hinges apart, remove the old grease and grind a tiny bit away inside the coiled spring with a dremel.
This will make the hinges go smoothly again and put less stress on the fragile plastic standoffs.