Sure, the Noragami manga is completed. It was a great ride with an ending that wrapped up the plot nicely. If you haven't read it yet, it's worth giving a go.
Yes, there are some out there. However, 'lemon' in fanfiction often implies adult - themed content which might not be suitable for all audiences. You can try searching on some fanfiction platforms like Archive of Our Own, but be aware of the content ratings and warnings.