Just because there are 4 searches per day doesn't mean they will all end up on your site even if it is in the top-10 results, which is a big if. Also, 50% conversion for a parked page is pretty ambitious. I wouldn't reg it as an attempt to make money with such little potential traffic unless you think it has a really good chance of getting type-ins or you think the ads will have a very high CPC. Check
SpyFu to see what your keywords will likely pay.
By the way, OVT results are per month, not per day. Did it actually come up as 120 on OVT and you just divided it by 30? Or is it actually getting 4 searches per month?