My partner is beginning to revert to Islam - looking for guidance, please

Assalamu alaykum - I’m hoping for some honest advice. We’ve been together since the start of last year and recently he told me he’s starting the process of reverting to Islam. I love him and plan to marry him, and since he opened up about his faith our conversations about marriage have become much more serious. A bit of background: I’m agnostic leaning toward Christianity. I grew up Catholic but drifted away in my teens after some hard times. Lately I’ve been feeling drawn back to religion, especially after talking with him. He isn’t pressuring me to convert, but I worry that my interest in learning about Islam - and the thought of possibly believing and worshipping Allah - is motivated more by wanting to please him and secure marriage than by a sincere desire for a relationship with Allah. That scares me because I’ve heard that insincere faith is a big problem. I don’t know how to work through that feeling. I also fear losing him. I worry I might lead him into sin or fail to support his faith the way a Muslim wife might. What if, when he joins a community or starts attending a masjid, people there encourage him to be with a Muslim woman? I truly want him to find community and support, but the idea he might leave me for someone else hurts. So I’m looking for practical guidance. How can I support him now, aside from avoiding tempting him with alcohol or sexual intimacy? Are there things I should be doing or learning to be a supportive partner without rushing myself? Has anyone here been in a successful interfaith relationship that led to marriage? Also sorry for using the term boyfriend - I know that’s not ideal in Muslim contexts, but this is all very new to me and I’m not sure what label fits yet. I’m open to all honest feedback, even if it’s tough to hear. Jazakum Allah khair in advance for any advice.