No. 2 in your list is a perfect opening for bundling. The median income is something like $50k so 3% would be $1500. Not chump change but not all that juicy. However, you get together 100 of your like minded friends on an issue, have a fundraiser dinner and invite the candidate to speak. Now you're talking about a $150,000 donation, comprised of 100 $1500 checks, from the "Lobby to Fuck America for Our Personal Profit."
But that's just for that particular candidate. Next, the LFAOPP will have a fundraiser for the political party that supports that politician. Politician will point out he never took any money beyond the legal amount, and the contributors will honestly state that donating to the party is not the same as donating to the campaign. Honest for weasely senses of that word, but perfect for court.
And after that, the LFAOPP will fund a "think tank," i.e. a marketing organization that will independently support its candidate with additional monies donated by its members. Our humble honest politician will correctly point out that he only took the legal amount of contributions. Contributors will point out they only donated the legal amount to the campaign. This think tank is a separate organization free to buy whatever advertising it wants to because Politician's campaign has no say in what it does.
I don't know what the solution is. Something needs to happen, but just limiting the amount people can donate is not going to work. At least not in the way we hope it will.