I think the acrylics are a great glue and use 'concrete bonder' all the time to ensure that one layer of concrete or plaster sticks to another. The old time masons I work with say that they used to, and still do, just 'paint' on a paste made with pure cement powder and water between layers. I would use cement as the bonder if the surface had to breathe - but my fresco panels can breathe from both the front and back, so I do not forsee problems. You can also use the bonder in the final layer, if you purposely want lots of cracking in the surface (using too much lime in the mix), but want to make sure this layer does not peel away.

The white cement in Canada is made in Canada, but the Asian one is one the market too, both are more expensive. White cement is about 30% stronger than grey portland cement, and it takes pigment well. I have some materials coming which advocate sodium silicate liquid in concrete, will have to see what they say.