Definitely cant be done because once you deposited / creditted a bonus to a user then the user is free to withdraw whatever amount that he has on his moneypot's account. Bitcoinrush will has no previlleges over the funds unless it is depositted into the app and moneypot has no feature to put in some "wagering requirement" before you can withdraw the funds ( and I dont think it will ever be )
Dont expect too much from this, unless there is a constant exposure of your campaign then the result by doing this will pretty much be a waste of resources
You are getting few wrong points.
#1. The maximum profit is tied to the Moneypot's bankroll which is currently 211 BTC
Therefore because it uses a kelly criterion ( depends on the site's house edge ) then the max profit that the site could give would be around ~200,000 bits ( thats 0.2 BTC )
#2. Giveaways and the other promotional stuff solely comes out from the pocket of the site owner and isnt funded by the investor's of Moneypot or the players because players' lost will goes to the investor (most of it around 99.9 %)
Ifyou use moneypot api for your casino u can just provide max profit to players of 0.2 btc. Its very low.