What is the expiation for complaining verbally about Allah's decree, and what is the ruling regarding a person's feeling that he has become close to disbelief and hypocrisy after uttering such words?

Since you have repented from this objectionable statement, your repentance erases the effect of this sin, and you return as one who has not sinned, for "the one who repents from sin is like one who has no sin." So, if your repentance is sincere, and you regret this utterance, then praise Allah and ask Him for success and steadfastness. Increase in good deeds, for "indeed, good deeds do remove ill deeds." Be certain of Allah's justice and wisdom, and that He does not wrong anyone, not even the weight of an atom. Listen to the Quran and reflect upon its admonitions, and do not abandon obedience; rather, increase in it, trusting in Allah's pardon and generosity, and having a good opinion of Him.