about to mean
so as to affect, you would also need to use the auxilliary verb 'do'.
It is in line with the idiomatic expression "do something about"
to take some sort of action to correct (a situation) We need to do something about this problem.
If you look at the example sentence given from the Oxford Dictionary link you provided in your question:
- there's nothing we can do about it.
this means that there is no action we can take which will affect the situation (we would like to affect)
Note that there are further example sentences in the Oxford Dictionary link (click on + more example sentences below the first example)
- We now have a better understanding as to why the firm is not accelerating in a growing marketplace, and what it is doing about it.
This means they have a better understanding of why the firm is not accelerating, and what action the firm is taking to affect the situation (probably actions which will improve the firm's performance)
- The system is rubbish, but there's nothing I can do about that.
In this case the writer is saying that there is no action they can take which will affect the situation - like in the first example you gave (perhaps taking steps to improve the system by making it better)
In your own example sentences, 'about' is being used to mean 'concerning'
If you replace them with 'concerning' they will still make sense, but won't sound as natural.