I'm only getting 365fps Max, 7gr, out of my HW75, seems a little on the weak side?
Yep, that's about right. I regard mine as a 10m target pistol and that's (energy) more than enough for that purpose.
When I last chronoed mine, it was only slightly more than yours. Does it leak audibly on the compression stroke? If not, then it's probably OK.

HTHs