Well, I've seen the advice given to you by the LFS mentioned by someone else in another thread (not sure where atm) and it was shown that trying to lower the temperature and salinity in an attempt to bring the dissolved oxygen level up in the water was actually more stressful to the tank inhabitants than the lower than 'normal' oxygen levels.
If you're running a skimmer then you should have more than an adequate amount of dissolved oxygen in the water due to the bubbles aerating it. If I were you, I'd bring your temp and salinity up to 'normal' (i.e. 78-82 degrees/1.025 salinity) your tank should do fine.
I wish I knew the scientific reasoning behind this, but from what I understand oxygen can only saturate to a certain point in water anyway, and with the bubble-action of the skimmer plenty of oxygen is available even at higher elevations...
That's my $.02

HTH