Finding Niche Marketings (keywords that are searched for)

I've discussed variations on this questions over the past several weeks, but have learned some new things, please allow me a moment to share what I learned, and look for some feed back.

I very much apologize in advance if I am repetitive here, but I am still really stuck and just don't know how to choose my next niche. I've learned tons of great marketing / site promoting things from members of the site, and WSO's I just need to figure out where to apply them (which niches).

1. I have a site I am holding the #3 position for in google US. (Yes this is verified, no local results (local search is off and position verified by other warrior members) or anything like that, I am really holding #3).

2. Google Keyword tool says there are 70,000 EXACT US (local) searches per month for the keyword I am ranking for. (That is about 2,300 searches per day).

3. I get 20 visitors per day from google from this keyword being in the #3 position. Does that many any sense, out of a supposed 2300 searches less than 1% of people click on the 3rd site in the results?

We had discussed these points last week here in a similar posts, but here is the new information I have gathered / learned;

I've run an adwords campaign to measure the traffic on this keyword. I ran it for the last 4 days, and I see an average of 125 people a day that search for this keyword, based upon the ad words impressions. Putting it around 3,500 searches per month.

1. How can google tell me there are 70,000 exact searches per month for a keyword that I have confirmed is around 3,500 search per month using adwords impressions to measure?

2. And the Million dollar question: What can I do to avoid this in the future - i.e. where can I get accurate search volume info without running an ad words campaign for each keyword I want to check? - That obviously not only can be costly buy can be extremely time consuming.

I spent several thousand dollars putting together and promoting a web site that I thought had around 70,000 exact searches for per month. Now that I find it only gets a few thousand searches per month, I don't want to call it a complete failure, but it is pretty darn close. I may be able to optimize it for additional keywords, but it still looks like the niche may be too small to get good results for a forum.

I am ready to move on NOW and start creating more sites in other niches, but I need to find a more accurate way of telling what the search volume is for a key word before I invest huge amounts of money in creating a sites / forums.

Please, what is the secret here for accurate keyword research, or tell me who I have to pay or bribe for accurate information. :-) I'm investing a lot of money in all of this, and if I have to buy another too for really accurate information, so be it, but I need to know it is fairly accurate, so I don't get Scre**d again.

Thank you for your patience with helping me through this extremely frustrating experience.

Jamie Dolan
Neenah, WI