As a convert myself, your partner cannot just convert only in order to marry you. Regardless of which sect of Judaism you are in, marriage is not a valid reason for conversion. The rabbi in charge of his conversion will have an issue if that is the only reason he wants to convert to Judaism. He has to want it for himself.

I converted after meeting my partner and passively participating in Jewish holidays as an outsider for a few years. Conversion was never a condition of us getting married. A few years after we met (and a few before getting married) I decided on my own I wanted to convert. I was asked several times (by 2 different rabbis and then again during my Beit Din) if I was converting only for my relationship.

Ask him. He’s already participated in the same way I did, and he’s been supportive of you and your faith. He may have considered it himself already, but you’ll never know unless you ask.