hmm, what happens to the Questioner's funds. Are they locked in for the bounty? Let's say the questioner doesn't mark the answer as "answered" and different answers get more than 10 "community" votes. Will the Questioner get a "refund" of sorts, if they feel like the question wasn't answered properly? Also, What's stopping the "questioner" from creating a new account? e.g often a "code" solution will be a real one. It will actually resolve the issue of the "Questioner" what's stopping them from creating a new account? At least with the case of a "Merit system", the person who wrote the code from scratch to help them will have a guarantee of sorts that their efforts will be rewarded. Your whole idea behind this website is people getting paid to answer questions, right now it seems like one side can get away with solutions without really rewarding the deserving user... If the funds are being locked in for the bounty till it gets marked then a "merit" like system could help.
E.g People who will get their answers marked as "answered" will receive these special merit points which they can use to vote for answers from other users. 10 points from other developers could mean it's the perfect solution for the problem.
As for 25%, I feel it's a bit on the upper side. Most Popular freelance platforms keep 20% at max. Maybe consider dropping a bit. Also, there needs to be a FAQ page. This sort of information should be available. As for the Design, TBH you can find many inspirations from just doing a quick google search
You should try the site as there are multiple disclaimers that appear at the relevant time to explain how the system works: including fees, payments, etc. So yes those explanations are already there and transparent.
But for your first criticism. I cannot force people to pay, as you imply by your question about refunds its their money until they choose to pay. And yes there are refunds as long as a response has not been marked the answer already. I've answered this question actually several times, but if you look at ebay they use a similar system as mine. Users have a points system, a reputation, and people choose whether or not to do business with them. On ebay it is also possible to just create new accounts and continue scamming as you say, but for some reason the system works and people continue to choose to use it.
The rate is my choice. And people will choose to use a different system if they think its too much.
Ultimately what I'm saying is that I disagree with your assertions. People aren't as evil or dishonest as you imply. And if the system, as it is now, is too loose for some answerers--again I'm transparent about it so people should go somewhere else.