Gigs can tolerate and actually like a lot of light. Typically they can be found in only a few feet of water. In other words, you probably can't give them too much light. I recommend the equivalent of a 250 watt halide. My gig used to sit right underneath a 250 watt 14k bulb, but also likes the Radion LED I have now.
In terms of flow, as others mentioned, they like strong but indirect flow. In your case, you can use both powerheads and face them towards the walls of your tank so the flow bounces off and hits the anemone from multiple angles.
Ideally, you want the gig to remain on the rock structure so the entire oral disk faces the surface. However, I wouldn't try to move yours since it's still acclimating, and if you choose to try to move it later, be very careful not to tear the foot by applying too much pressure as you try to remove it from the overflow.