I'd use a CO2 tank oring for the Spyder VA, vertical adapter (under the barrel), and wipe out the lower tube and put the oring on dry. I've found these seal better this way 9/10 times, the other time a little oil or grease like you should with the black ones.
The hiss or leak out of the barrel could be a couple things. All blow backs 'leak' if your uncocked when air up, and tend to hiss for a couple shots. So if it stops, not to worry. If you fix the other leak and it still hisses out the barrel its probably the cup seal, they dry out or whatever and don't seal anymore.