Hi,
1. The spawn points let you decide the initial shape of the rope, so the number of them that you use is totally up to you (it doesn't influence the performance in any way, the resolution and total length of the rope does however).
2. Is your ground a non-convex mesh collider perhaps? See this under "Current Limitations" above:
Collisions work with convex Mesh, Box, Sphere and Capsule colliders only
3. That's exactly a use case for multiple spawn points. If you need more fine-grained control of the shape, I suggest that you spawn the rope and then set each particle position using a custom script (for that you can see what functions to use in the README).
Hope this helps! I'll be away on vacation for 2 weeks starting tomorrow so if you have further questions please send an email through my website and I'll get back to you when I come back.
/Gustav