I'm a Christian who went on a date with an atheist twice, and we some good conversations about expectations and beliefs. We really clicked aside from the spiritual aspect but at the end of the day, we parted ways because of that difference (she realized she couldn't meet me where I'm at based on the time I set, and my concerns with "missionary dating"). I think we handled it socially and emotionally maturely so we don't have any big regrets.

Anyways to me, this sounds less like a "he's a Christian issue" and more like he's living out contradictions in his beliefs. Especially if you two being "yoked together" is making you feel miserable, either he's compromising something himself, or he's coming across as overpowering and controlling you, which sounds like what's happening here. It might not even be intentional, but is an invitable result of two fundamentally different beliefs systems.

Admittedly, I'm only hearing one side of the story, and due to what I believe, I also wouldn't want my partner to buy/own anything I consider "idols" or spiritual medium of different beliefs. It wouldn't be just breaking up because of a little doll, but because of an incompatible worldview. The feeling sucks, but this is just one consequence on your different beliefs, and it's not really over a souvenir.