SEO, PPI and more

Hello,
i have made around 30 different software applications that i monetize with PPI and have a couple of questions.

Some of them are good, they have been reviewed by PC World Magazine, PC Advisor Magazine, Download.com , Betanews e.t.c. .

The problem is that i have little knowledge of SEO.

I get around 15,000 installs per month total.

The problem is that i have only 43 visits per day with organic search !
All the other traffic is from download sites such as download.com,softonic.com e.t.c. .

I have around 450 finished installs per day.

I have bought Rudenko's Robosoft and send my application pad files.

Do software developers get most of their installs from Download Sites or Search Engines ?

I recently got a subscription to woorank.com to boost my SEO.
Do you have heard of this site ? Is it good ?
I will try to fix my site with this tool.

I want to buy also SEO services but do not know anyone who is good at it , and that does white hat practices only. I also hesitate to hire someone because i have heard that good SEO services cost more than 1,000$ .

Also my webpage is hand written in php and jquery . My skills are mainly in .NET programming and not php.

I monetize my installs with InstallMonetizer .

I am quite happy with them, despite the fact that they recently reduced the revenue that is generated.

Do you have heard of other PPI programs ? Are they better ?

I like InstallMonetizer because they do not use a download manager where the user has to wait to download your application but they bundle the offers within the NSIS installer script.

Also, the bundles are located on their servers and not on your own. This is good in case they get blacklisted from AV companies.

Thanks !