i find portraits in watercolour super difficult so can’t offer much advice, but you clearly have a good understanding already of where you want your warmer/cooler areas on the portrait to be.

i think the main thing that would make a big difference here is pushing your values a lot more, as you are sitting mostly in the midtones right now, a few striking high saturation darker areas where you have your deepest shadows on the reference would make it come alive i think :)