I don't see what could be wrong in promoting this kind of things like huge jackpots since people love them. The same thing happens with national lotteries that offer jackpots a lot bigger than this and nobody says anything about them. Remember, it's ALMOST impossible but not 100% impossible and the same thing we can say about all lotteries that offer a huge jackpot. And even though the chances of winning are probably as low as 0.00001%,there are many people who have successfully won those kind of jackpots so we know for sure that its possible and it's just a matter of time until someone is also going to win this Primedice jackpot.
Regarding terms and conditions being edited or removed, again its a normal thing. Every gambling website proceeds the same and it's their right to do whatever they want since it's their money they are offering. I am pretty sure the terms are not going to be changed after someone wins the jackpot just to make sure he is not actually eligible for it because that would be fraud,but changing the rules and terms during an ongoing competition or jackpot is absolutely normal.
I mean why wouldn't be ethical? Aren't they really giving out that jackpot? Isn't it just there for the taking? The odds doesn't really matter, you can definitely win that amount mathematically which means everyone has a chance to actually win 112 bitcoins and that is all it matters, what were you expecting ?
To have a 50% chance of hitting a 112 bitcoin jackpot? That is not how you reach to 112 jackpot at all, the harder it is to actually win the higher the amount gets, now that the amount is amazingly high it is amazingly difficult but that doesn't make it untrue. Just because the odds are not big doesn't mean they are not giving that money away.
They ARE giving away that much jackpot, and even with small odds you still have a chance so if you have a chance to get it than they have a right to promote it.