Re: The Golden Ratio Attack. Blocks more than half full lead to mining monopoly.
Good post, totally get the math... all in on the theory...
Thinking it over a bit (beer++)
Let's work the math. If 2/3 of the transactions actually processed are "real", then whoever is maintaining the backlog is paying the tx fees for 1/3 of every block. If this is someone with half the mining power then they get half of their third back, so their average cost per block is the fees for 1/6 of the block. If we are talking about someone with half the mining power, their average return per block is 1/2 the fees for a block. Because 1/2 is greater than 1/3, they are making a profit.
I think I found your bug....
You fail to account for the revenue of the other pools. You state the profit per block won but not the loss per block lost.
Proof:
In the end the spammer (Bob) ends up making more money for the honest miner (Alice).
It's a zero sum game. Bob is the only one dumping extra money into a system that both Bob and Alice draw from.