Is it permissible to equate love for Allah with love for His Messenger (peace be upon him), or should love for Allah come first, then love for His Messenger? And what is the ruling on seeking forgiveness from the Messenger (peace be upon him) after his death, and is that considered shirk (polytheism)?

It is not permissible to equate the love of Allah with the love of anyone else. Rather, the love of Allah must supersede the love of all creation, for the love of anyone else is subordinate to His love. As for the love of the Messenger, peace be upon him, it comes after the love of Allah, and it is a subordinate love for Allah and in Allah, not a love alongside Allah. The love of Allah is worship, humility, and submission, whereas the love of the Messenger, peace be upon him, is a love because Allah loves him and commanded his love.