When people should have been suspecting Whirlwind to be scam is when they began anonymity mining or something with 12% APR.
There were questions about it:
Our goal is to grow the Anonymity Set to 10,000 deposits so until that is reached we will offer a reward to everyone using the service. Each month we will allocate 1BTC to distribute between all funded Notes proportionally to their balance. Payments will be made every day and you are free to withdraw your deposit anytime. If the amount allocated for rewards is 1BTC a month that means 1/30 = 0.0333BTC will be distributed every day.
If the multi-sig balance is 10BTC and you have a Note with a 1BTC balance you will automatically receive 10% of 0.0333BTC every day you keep your Note funded, which is 0.0033BTC a day.
On second thought: this sounds a lot like the many "services" in the past that paid interest on Bitcoin deposits. Usually, that didn't end well.
Are you sure you want to be associated with those?
Do you have any example of a service that had an actual reason for offering a reward on Bitcoin deposits?
The goal of this campaign is to grow the Anonymity Set
I think their "anonymity set" (which means the total number of deposits) was around 400 at the time. So, by offering 12%, they only managed to get about 1 deposit per day since then. Maybe people recognize when something is "too good to be true" by now. At that rate, it's going to take 25 years to reach their goal (of 10000 deposits), which makes it clear things didn't go as they expected.
$40k in DAI
This is from the review campaign, isnt it?
Should this sum only be used to pay out the unpaid contributions from the Bounty campaign ~ or if someone used the mixing service and still waiting for the withdrawl?
It wasn't very clear, but I'd say it was implied it's okay to use the $40k to cover the risk of the anonymity mining. See
these posts. The money in escrow was initially meant to cover the review campaign, but wasn't asked back. After that, whirlwindmoney agreed to add a 7 day delay if they ask the money back. Come to think of it: this delay could very well be the reason the money is still in escrow and
this scenario was prevented. You're welcome

I don't see the problem here, it's money from ww, it shouldn't be a problem if it's used to cover the mess they made
Agreed.
the unpaid promised interest (12%)
The EU bank guarantee stops paying interest the moment a bank goes bankrupt, but you'd get interest until that happened. Considering it is at most a few percent, and considering how complicated it will be to calculate (and prove) the exact amounts, I'd say forget about the "interest". But I have no skin in this game.
Can WWM manipulate notes data, such as changing balance to zero or creating fake notes and claiming part of the $40,000.
Of course. They can create and sign any LoG they want. Or even make a real deposit through their own site, and use that deposit to claim the majority of the $40k.