Try defining the BuildRoot
variable in your spec file. The find-debuginfo script looks in to that directory several times, and will die without it.
This will usually look something like: BuildRoot: %{_tmpdir}/%{name}-%{version}-%{release}
As to your second question, I can't say without seeing spec file and sources directly, and I am by no means an RPM expert. I will recommend you to Chapter 13 of Maximum RPM(there are copies available free online), and the notes from Tom Callaway's presentation on How to make good RPM packages - I've found the spec examples here to be very helpful in the past.