IMO the skimmer is the one piece of equipment you do not want to cut corners with. Always try to get one rated for a larger tank than you are going to use it on.
I agree that this is not the right skimmer for your tank. I use one on my 150 gal reef tank, It does an OK job but I'll be upgrading to a Euroreef soon. I have a deep sand bed very few fish and feed only 5x a week. I don't have any algae problems or nitrates so it not the top thing on my list right now.
No. It is bad enough the manufacturers of skimmers overrate their capacity to begin with. Never go under if you are going to have any bioload whatsoever.
