Hi Chris,
In my experience as a barista trainer, I find this issue quite regularly. I love your details and how you outlined a lot of what of true and correct facts.
Long story short, my suggestion to you would be to pay attention to your slow pouring. Before rushing through to finish your piece of art, finish your tulip stack or rosette with a bulb (round) heart and lift away from the cup before dragging a thin string of textured milk through your design like the finishing brush stroke on a canvas or intricate art. It seems your designs are very rushed also which is also the reason for not getting fine line artwork such as a 12-15 stacked tulip, or a swan/Phoenix.
When you drop your jug for the first part control the speed and ensure its super slow which should stop the likely food of the cream splitting away, no matter how thin the crema or milk is. You should be able to pour any style of milk in a flat sitting cup and not disturbed the crema, essentially laying a bed of froth under the crema to help lift it to the too. This combined with slow pour results in great latte art.
I hope this helps and I look forward to seeing the results. 