There is Spotify addon already in LE repo. Try using it.
Re WP2 build, please try using Raybuntu's build: images My build was only trying to inject WP2-specific patches to S905 project, I guess this is not enough.
Re playback issues, Amlogic hardware playback is still being worked on by Kodi developer Peak3D and tested intensively by me and other developers. As soon as there are no issues obseved by me in this PR, I will make a public build: AML clock timing adjustments by peak3d · Pull Request #10887 · xbmc/xbmc · GitHub
Isn't that for Spotify connect from your phone ? My link is a Spotify addon for Kodi (no phone needed)