I would say that the contest still has to end if nothing at least because of the sponsor. (sounds like a serious sports competition)
If the contest is suspended so the sponsor deals too. There are no point to run a contest which is obviously is not serving a fair purpose. It's clear that some sort of manipulation and incentivized with merit. The sponsors can do the same for the next event if they are still interested. Fortunately for them, with this one they got some free advertising for sure.
So, what about merited voting posts? whether they will be taken into consideration or he will be suspended like the one who sent the merit?
if it will be such a strict rule I can give merits to random posts, and influence, for example, others to be rejected.
Fair enough, maybe ask admin to disable meriting the post at all. Or give a bold warning that if one sent merit and found abusing the rule then DT members will be requested to tag them. At least this will create so fear in their mind. And if anyone dares to brake the rules then as the rules said, give them a paint in their wall.
Point is, give enough warning so that they do not abuse the good initiative.