The bet % matters because if there were 1000 bits bet at the normal percentage, I would be able to complete the giveaway. This isn't really 'fair'...
On a separate note, the site is up. Are you viewing on mobile? Try desktop or a different browser. Also enable javascript.
The house edge on every bet is the same. It doesn't matter if someone bet @ 1% or 50% or 90% or 99%, you make the same amount.
You said "make a bet and I'll give away money" with no other qualifiers. Someone made that bet and should rightfully expect the promised money. If you do not deliver that looks quite shady. In the future you should explain your promos in detail.