Maybe I will just keep the minimum amount of assets to get the bonus on the cards.
Your situation definitely sounds poorly handled. I've only been with BofA for a couple of years, but I've maintained low expectations due to data points such as yours. Haven't needed their help so far.
The way I have my Merrill account set up, they make $0 from me. Couple that with the cash back I extract from them monthly, and I'm a net liability for them. I assume the ≥90% of FT customers are money losers for their banks as well. The question is: If I don't like BofA, but they're losing money on me, should I stay or leave?
Another workaround for you might be to change your 3% category to something other than online purchases, dining perhaps? Or maybe work on getting a second CR and try to extract more cash back from them? At least you learned the lesson pretty cheaply that when in doubt, just return the item rather than rely on BofA to cover your 6.