Well, in fact all these things are a matter of consensus, of power to apply and of personal ethics.Your logic is generally correct, but here are some exceptions :
In 1 : if I leave the country without paying the bill, the obligation cannot be enforced. So is it an obligation then?
In 2 : if I promise to get revenge, then it may be more moral not to keep my promise.
Things related to ethics cannot be hard-coded into definitions.