What is the ruling on combining and shortening the Maghrib and Isha prayers late at night, and what is the ruling on one who mispronounces the glorifications in rukoo’ and prostrates for forgetfulness fearing the invalidity of his prayer?

It appears you have many whisperings (waswas), so disregard them and pay them no mind. Your shortening of the 'Isha prayer after returning from travel was incorrect, so you must repeat it as four rak'ahs. The time for 'Isha ends with the rising of dawn, and it is not permissible to delay it past one-third or one-half of the night without an excuse. The intention for prayer must be determined in the heart without uttering it verbally. An error in the glorification during bowing (ruku') does not invalidate the prayer, nor does it necessitate the prostration of forgetfulness (sujood as-sahw). Your performing of the prostration of forgetfulness out of ignorance does not invalidate the prayer.