Interfaith marriage issue

My fiancé is Jewish by birth. He decided earlier this year to start actively practicing the faith. I was raised Eastern Orthodox Christian but I no longer practice any faith. I identify as agnostic at best, but lean towards atheism. However, I believed that it would be good for my fiancé to get involved with and embrace his Jewish heritage. I fully supported him going to services, meeting with the rabbi, going to the Torah study groups, and being involved with the celebrations.

My fiancé has struggles with mental health issues his entire life. The last several months have been particularly hard. About a week ago, he went to Torah study, and then visited with the rabbi and discussed some of the recent struggles. The next morning, he told me that the rabbi encouraged him to leave, create space between us, and get his own place.

I have three children, we don’t have any children together because he is unable to have kids (we tried for over a year), but my fiancé has been a father figure to my kids, as their biological dad is not in the picture after losing his parental rights. The rabbi knows that we have a family.

I don’t know what their conversation was, and after having him leave the day he informed me about talking to the rabbi, he has since had intense regret and wants to come home. I was very upset when I found out that he chose to act on the advice of the rabbi when he told me he was going to leave, especially because they have only met each other a handful of times. When talking yesterday, I told him maybe he should talk to the rabbi and ask him what he should do now. My fiancé informed me “The rabbi thinks I should marry a Jewish woman.”

I was completely blindsided by this. I initially thought that he was told to leave because of the struggles happening at home as a direct result of his mental health. There has been a lot of arguing. When my family and friends asked me initially if it was because I’m not Jewish, I was confident in telling them that I didn’t believe that was the reason.

I’m not sure what I’m asking here. I guess, is this normal? Is it typical that a rabbi would tell someone to leave their family and find a Jewish woman? I grew up Utah, and the LDS emphatically encourage their members to marry within their faith, but even the interfaith LDS relationships I have had in the past, their leaders have never told my partner they should leave and find someone of their own faith to be with. I am no stranger to being the outsider in religious communities, but never have I experienced anything like this.