When it comes to LPS, they need to be around the bottom of the tank or in a dead spot in the upper section of your rockwork.
Orient the Tunzes so they don't blow on the LPS, either by raising them up, leaning them upward (like I did with a chunk of acrylic), or pointing them to the right or to the left. Using your controller, you can ramp them up and down every 7 to 10 seconds, cycling the flow between the two so that no coral is just hammered non-stop.
Billybeau knows more about ORP than I do, but to me it basically is a number to gauge how well the water is doing in my tank. When the water doesn't hold a lot of organics, ORP is higher. Running fresh carbon in a Phosban Reactor (active filtration rather than passive filtration), ORP should rise within 24 hours. A new water change should bring ORP up within 24 hours as well. Feeding the tank, not changing water, or adding some additives (Chemi-Clean for example) will make ORP drop.
290 - 310 is fine, Steve.