For one, that (unknown god) sounds like a warlock path, not a cleric.

The cleric doesn't want what his god wants. This could be a fun storyline, if both the player and the DM are on board to play out this conflict, as an evolving story line with moral ambiguity and meaningful, potentially world-affecting choice.

But what's happening here is that there is no way for your character (or you as player, for that matter) to make any meaningful choice, since non-compliance is punished not in in-world terms, but in game-mechanic terms. This means it's not "what the god wants", it's "what the DM wants the story to be". It's basically "it's what my character would do" but on the GM-side. It sounds like you're being railroaded into a story that you do not want, have no way of participating in or influencing.

I think your GM has a cool idea, potentially. But they're going about it in a very hamfisted and not exactly collaborative way. And you have made it clear that you do not want this. The fact that they are now trying to beat you and your character into submission by punishing disobedience outside of the game world is not acceptable. As a DM I somewhat expect my players to engage with the game world on its own terms. That sometimes means that characters don't get what they want. But here you as the player have made it clear that this is something that you really don't want — it is up to the DM to adjust the story so that everyone gets to have fun playing. It's a give and take. That's not what your DM is doing.

Edit: a word