Is feeling love for the Messenger (peace be upon him) more than for Allah, or fearing loving one's spouse or children more than Allah, considered an act of disbelief that expels one from the faith and necessitates uttering the Shahada?

Worrying about disbelief (kufr) must be entirely ignored, and it does not necessitate leaving the fold of Islam. A Muslim does not believe that supplicating to Allah by clinging to Him alone implies a lack of love for His Messenger. Rather, part of loving Allah is loving His Messenger. What is prescribed is for a Muslim to ask his Lord for His love and the love of those whom Allah loves. Prioritizing the love of other than Allah over the love of Allah is not disbelief in every instance; rather, it may be a great sin, but it does not lead one out of the fold of Islam.