It is not a problem at all with Ethereum's smart contracts. It is possible to make 2 in 1 - ICO and DAO smart contract.
Yes, all contributors wallets (addresses) will be stored in the blockchain.

I think at this moment 20% of profit is not a very attractive deal if people provide 100% of capital in your project. There are many project that distribute 100% of profit among token holders (founders keep some percentage of tokens to get their share).

Good luck with your project!