Sí hay reglas. Estar significa «to be in the state of». En otras palabras estar refiere a una condición o un estado. Ser refiere a una cosa mas integral, mas permanente.
All the sentences you presented are completely correct but in many cases, the sentences can be used with the other verb but with different meaning. For example: «La ropa está usada» means the clothes are used as in second hand. But,«Está ropa es usada por negócio» These clothes are used for business. Ser refers to something inherent, while estar refers to something temporal. I hope this helps.
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