Help with humidity/condensation issues

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Why would you keep the bathroom vent running 24/7? Exterior air is often more humid than interior, so you aren’t necessarily drawing in lower humidity air. Shut off that vent and run the AC.

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This,

You need to start to start with shutting off the bathroom vent except when the bathroom is in use. You are pulling in humid outside air to replace that being exhausted by the bathroom vent. If that doesn’t solve the problem, you need to see if the mini-split is functioning properly - is it properly charged with refrigerant, is it properly sized (not oversized) for the space you are cooling. A properly sized and functioning HVAC when operating for long hours should be able to keep relative humidity near 50%. And is there a source of outside air infiltration into the enclosed and insultated area you haven’t accounted for? That can be determined from a blower door test.

Is the living area insulated from the shop itself? Or is only the structure envelope insulated?

Both are individually insulated. Plus dry wall in the living quarters

It sounds like you have multiple issues. The vapor barrier issue is something you need to address, though there is no perfect fix. You could use a product like redguard under all flooring, but you still have the bottom plates wicking moisture. On that note, did you use a sill sealer under the plates?

I don't know anything about your site conditions, but depending on your slab and site you may never get it dry as-is.

Yes to fan off and check AC operation. In addition dis you put a vapor barrier under the slab (assuming slab). If not you will get moisture through the slab. There are products to put on top of the slab that will serve as vapor barriers.