b) the law had to cover a lot of usecases and in order to do that concisely, it may sound vague in places. I also don't like (developers never like uncertainty), but there's established practice already in regulators and courts about what is considered "adequate", "appropriate", etc. I agree it could've been better though.
c) that is happening already, e.g. ICO (the UK regulator) has a pretty good set of guidelines and examples. There's also the process of "prior consultation" where if you are not sure about something, you go ask your regulator for a decision
d) this is exactly what the "proportionate", "adequate", etc. are in for. If you are a small company with 2000 data records, you are not posing a high risk for the rights and freedoms of data subjects and so most of the things are not a strict requirement