You have to provide all the documents and then you have to submit it so basically you are paying the agent to review what you're submitting. That doesn't seem very cost efficient. I think agents are more valuable when they're doing all the leg work for you.
I believe the 500k needs to be in the accounts for at least 3 months and I also am curious if they are looking at salary amounts. They may be rejecting on monthly salary amounts. I've noticed people that are around the $2,500 a month mark have been getting rejected. I have no idea if it's related but it would be interesting to see how many rejections are in that range for monthly income.
Think of it this way, you're going to have to provide most of the paperwork and the agent is only going to review it and then you have to go somewhere to submit it. So you're really paying him a thousand-year-old to review your own documents that you are creating.
As for the school, you're probably better off picking something that you like and will actually do. That way if immigration ever questions you you will have proper answers.
I find the post humorous, not because of the context but rather the content, specifically the sentiment that the OP isn't gullible and can spot a scam a mile away. I'm pretty sure everyone that has ever been scammed in personal or business dealings felt the same way until they didn't....