That outline is not level in the Z axis, i guess that so by purpose.
In general I would say that the layout is too complicated to get that shape into a surface in one step.
You may want to try to do that by breaking that shape into multiple parts and then join the resulting surfaces.
Also, if you can get rid of the distortion on the Z axis would be of great help.
In a short try I was able to turn at least a part of your shape into surfaces. So the rest shoud be possible too.

Regards
Heiner