Ideally it should also explain why some situations are ambiguous and why the more specific tagging is needed/better, and in this context maybe also describe why some exceptions to these rules are still widely in use and/or accepted (if they are). Otherwise the wiki won’t be taken seriously. But again none of this will be of much use if there is no scheme most people agree with and to arrive at this a deeper look at the data will help as pointed out by @osmuser63783 above.
Yes. Or even better vehicle:backward=false. But I guess this is just a fantasy. However, it does help my understanding to simply think of oneway=yes as synonym for vehicle:backward=false.
I can sense the sarcasm, but just to be sure using a relation or node tags for something simple like a oneway constraint would be a terrible idea regarding simple consumption of the data (which I think is something OSM should always strive for).