> cap individual donations

Direct contribution cap for individuals is $2,700

> forbid companies from donating

Direct contributions are not allowed, although PACs can give up to $5000.

> create a government entity whose goal is to ensure donations are respecting those rules

Aka the FEC

> candidates having to deliver their list of donors to said entity

Already required for federal elections, also candidates must detail how they spent the money as well.

> Make it actually illegal to get private money from PACs and other complex setups.

PACs aren't complicated and for the most part are a positive step towards fair elections (that's why they were created in the first place).

> And eventually reimburse part of the campaign past a certain percentage of votes.

Federal elections already have public funding and the system in place is much better than reimbursement after the election.