[392Bird]

Sounds normal to me for a a/c system running in a near satisfied status. With it in this same condition, put it out in the sun, and roll the windows down part way. You should see the a/c clutch engage/release much less often, and keep working to cool the car. If it does not, then it may be slightly low on charge.

The hissing sound is normal as the system is going from operating with part of the system in a vacuum, and the other part above 200 psi, to all at the same static pressure.