What is the meaning of "Salafi"? Is it true that Muslims were not divided into Salafis or others during the time of the Messenger, may Allah's peace and blessings be upon him? And is the designation "Muslim" sufficient in this era?

Salafiyyah means following the methodology of the Prophet, peace and blessings be upon him, and his companions in belief and action. It is a methodology that every Muslim must follow and propagate. There is no harm in a person attributing himself to this appellation (Salafi), nor in cooperation among the followers of this methodology to spread it and call to it within a group, provided that loyalty and disavowal are not based solely on these designations. As for your husband, who is new to Islam, he should not be preoccupied with such appellations. Rather, he should be taught the true religion, and the leniency of Islam should be clarified to him, and he should be called to unity.