My mum converted to reform Judaism to marry my father (raised in the orthodox tradition , but about as un observant as they come). She absolutely loved it because she had never had any real formal education and for her she loved the scholarly side and being part of something. It was still a lot of work - she had essays to do, classes several times a week, she learned how to read Hebrew etc. Took about a year, all done in the evening while working full time
I was brought up Reform and she was by far the most observant of any of my family - my dad's side are all still in the orthodox tradition, but very secular. For most Jews, I about food and family (they tried to kill us, let's eat!).
I consider myself culturally Jewish but atheist by belief. My husband isn't Jewish, but we had a lovely interfaith Jewish wedding blessing that was to all intents and purposes a Jewish wedding ceremony, but of course wasn't recognised under Jewish law
My mum wasn't alive to witness our wedding, but before she passed she was very keen on the idea of my then boyfriend converting as she had. I said look, I don't believe in any of this religious crap, so how can I expect him to go through the whole megillah (Jewish expression for the whole shebang)?! We still observe the traditions, just without the G-d bit (old habits die hard!). We have Passover Seder with my family, or Rosh Hashanah dinner - I just don't go to shul as I used to do when I was younger. I light the Chanukah candles, and he joins in because we share the same values - it's carrying on the traditions of a people, they don't have to have massive religious significance if you choose not to view them in that way (although I still say the Hebrew blessings before I light any candles, which I agree is massively hypocritical!)
It sounds like your partner wants a much more religious Jewish family life - but just to say that you can choose a life that works for both parties if you're able to negotiate a way forwards. It is hard if you're fundamentally opposed on certain issues, which unfortunately means asking hard and searching questions up front
Good luck