Welcome aboard! Your post echoes many of my own feelings on the org.
If you're interested in the topic ( which it seems that you are) you should do some more research on cosmology, astrophysics, and evolution. You'll find that not only is the improbability of something insufficient to prove it didn't/couldn't happen, but the universe's existence in its present state is not nearly as unlikely as the creationists would have you believe.
As for your bulleted points, there is definitely some level of monetary scam to the org, and the GB and others definitely benefit from the many scams that they're running. They benefit materially, they get to travel the world and have their healthcare provided for them. They have absolutely no concern for their future as they will have their every need taken care of until the day that they die. This is a level of security and stability that the rest of us could only dream of, and is certainly undeserved by these men who create nothing of value for society - indeed they do little more than destroy lives.
Is the money the reason the cult came into existence? Probably not. Pastor Russell did fall into temptation pretty early on selling his miracle wheat and other scams - so there was definitely a monetary motivation for him. Rutherford continued this and lived quite extravagantly, he seems to me to have known exactly what he was doing. After Rutherford, the WTS had so much momentum and was run by men who themselves were indoctrinated into the cult so at this point it exists merely to continue its existence.
100% agree - the Bible is not from any supreme being.
As for your assertion that anyone who believes 100% is mentally deficient - I would suggest that you educate yourself on cult mind control and undue influence. Very smart people can become indoctrinated into a cult very easy when they're vulnerable. There are many here who are quite intelligent but were, at one time, 100% believers.
I hope you stick around, you'll likely find lots of useful information and great folks to help you in your journey. There are a few nutjobs here too, so take opinions with a gain of salt. I suspect you'll do fine. Best of luck to you in your journey!