If I understand this right you are taking the whole remaining pot and dividing it up depending on how much someone invested in?

That could work but you should probably pro rate it for fairness.

For example anyone despositing steem today 100% refund.
For each day take off a % because people were allowed to play and get money back versus the guy who just spent 1000 steem today.

If that is how you are going to do it, then I can see it being the most fair way to move forward with changes you feel are necessary and avoid scam and fraud claims.