It can be just right with the rotate tool. You only need to be careful with snapping to points, directions etc. Draw a flat plane, bring your objects to intersect with it and rotate with the intersection line as axis.

In reference to your latest illustrations, the intersect process will create either solid lines or hidden lines. In MY observation/experience, Sketchup/OpenGL seems to be trying to create logical faces. That is why you see all of those hidden triangles. If you have ever noticed, OpenGL shading(called either gooch or Gouraud shading, not sure which) will exhibit slight shade variations on faces with more than 3 edges, especially on smoothed models. The shade variations are "virtual" edges that will not display as lines, but tend to align with where a logical edge would occur between vertices. Your introduction of the cylindrical extrusion and intersect created virtual triangular faces. [I am not sure at what scale you are working, but it is important to remember that Sketchup does have difficulty with tiny faces, even though this does not appear to be your problem. I only mention it in case scaling also influences the conditions you are experiencing. As recommended by others, scale the model up as much as 100x for the modeling procedure and then by .01x when finished] Again, the above is MY observation/interpretation sprinkled with stuff I have read here and searches on the internet.

I think to create a developed surface accurately in SU, you would need to have a much higher number of facets than the model currently in question has. You would be better off modeling the curves without triangulated faces. The shape can and should be drawn without them and then unfold will look better. And you can do that without a plugin. That said, you should consider that the chine curves you have now are only approximations due to the long line segments between vertices and you'll need to make allowances when cutting out the sheet material. For a hull like yours I would be more concerned about getting frames at the stations built and then I would spile the planks from the frames. You could use Gregg Carlson's Hulls program to create developable skins. It would also do some basic hydrostatic calculations for you to give you an idea of its waterline at its designed load. what do you plan to use to skin this hull?