The "problems" you are talking about are not real problems of the game ...
1 - Everybody can only put 3 offers of sale and everybody has to pay 10 water lilies to put more
2 - the 10% crystals are to be paid by everyone too, whether you sell it or not. They are taken at the time of the sale.
3 - It is normal that you see players lower than you on the market, I do not know any player having a level higher than 417
