The film on the surface is a sign of not enough water movement from your powerheads. Try to point them up so you get plenty of surface agitation, and this will also help your gas/air exchange to help create a higher and more stable PH level.
Skimmer- yes, let the tank fully cycle. Iíd invest in a low range PO4
test kit, I like the Red Sea Pro. Once youíre cycled, and begin a feeding regimen for your livestock, that would be a good time to start the skimmer up. If you donít quite have a bioload, your skimmer will not produce anything. Keep an eye on your PO4
levels. Youíll want to keep these numbers in check, and this will ultimately help determine water change needs, feeding schedule, amount, etc.
Hope that helps.