Is my fork disc compatible?
Yes, your fork is disc compatible, but your hub is not. The fork appears to have mounting points for the older 51mm I.S. disk brake standard. See 

https://www.bikeman.com/bicycle-repair-tech-info/bikeman-tech-info/1638-51mm-international-standard-74mm-post-mount

for examples of the two most common styles of disk brake mounts.