I have used a 25w emperor aquatics uv sterilizer on my 75g for ich management for about 8 months now, and I think it really helps. Definitely doesn't irradicate ich, but it does help to really keep it at a minimum.
I agree that sounds like a very high flow rate. I run mine at 90 gph. You'll probably want to get a flow meter, they're like $30 on Amazon. If you run it too high, you won't have enough contact time to kill ich. But if you run it too low you won't get enough water passing through it to really kill enough of the parasite.
Also, I cannot recommend running it off your return line enough. On my current tank I run it with a maxijet, and it's just another thing cluttering up my sump that I have to clean and maintain. I'm setting up a new tank right now and a couple weekends ago I plumbed the new UV sterilizer off my return. It was really, really easy. I just put a T that branches off to a gate valve.