My usual strategy is to keep boil gravity from 1.040 to 1.050 which is a practice I keep from reading How To Brew by John Palmer. This helps with hop utilization for the bittering hops. Final gravity I keep around 1.060 because my experience is that with gluten free fermentables, less then that just seems a little thin.
And yes, I add things toward the end of the boil that I want to preserve the flavor. That is why the molasses and especially the buckwheat honey is added toward the end on the boil. Next in line would be the Belgian candy syrup. If I add some of the sorghum syrup at the end of the boil it is to keep the gravity lower at the beginning (usually for partial volume boil).
If you try this recipe, I hope you like it. I just put my 4th batch of this in the fermenter yesterday. I varied some elements in batches 2 and 3 but am returning the the original.