For search done directly on Searchtrade, Searchtrade is the "Application Developer" and hence gets 50% for such searches?

After initial pre-selling pool gets funded through ads, so if ads cannot generate sufficient revenue, the payments will go on decreasing per search rather than being constant.

And what about your results, will it be taken from more bigger search engines like google/bing etc. or you are building complete search engine(crawlers+databases+page ranking algos etc)