If the owner sends EOS to his own casino, to who
m will he lose 1,5%?

They will lose 70% of house edge(which is 1.5% of wagering amount) to rest of bet token holders.
You must remember all the bet token holders get the 1.5% house edge and the team only has the 30% of all bet tokens (unless they played as well) which means the shareholders will get it not the team. Hence, on generating fake volume, owners will lose 70% of house edge unless otherwise they have bought 100% of circulating supply.