As your curves have some different inflexion one to one it's some difficult to loft or Sweep with the entiere curves in one pass!
You must trim all and loft by loft and sweep by sweep
As there not yet Gordon curve or Coons curves you maybe must redraw more some new lines for closed cleanly your forms :)
Or "Show points" and move some pts when a sweep is made
Link file as speedy beginning example :)
I had not modify your original curves!

So maybe your start lines are not enough stream lines fluent :)