Hi David,
Just some notes... Your curves are kindof "scewed" around differently, which is making a surface structure kindof bent or twisted and can lead to problems.. Turn on control points for that surface and review them.. Getting them to be more uniform can help with your process further down the road.

The trimming curves doesnt go all the way up to the top of the surface.. If you look at the front view and zoom in, you will see a gap at the top area.. You could run extend on those ends to get them to go all the way up.. I could then trim out that area by extruding the curve through and doing a surface/surface trim... However, I would rework a few things here before moving on...

Lyes model may be something you want to review...