Is it wrong to complete the circumambulation (Tawaf), then pray Maghrib and Isha in a delayed combined prayer (Jam' Ta'kheer), then complete the ritual walking (Sa'i) after entering the Noble Sanctuary in Mecca after the Isha prayer?

There is no harm in separating the circumambulation (Tawaf) and the striving (Sa'i) with a break or prayer, as continuity between them is not a condition. Many scholars have permitted this; however, it is better to perform them continuously, following the example of the Prophet (peace and blessings be upon him). You made a mistake by delaying your Maghrib and Isha prayers until after the Tawaf. The correct approach is to perform the prayer before commencing the Tawaf.