Should I wait support? edit: added giveaway :D

if you no longer need support to do something, close your ticket.
if you go into your ticket, there should be an option somewhere ( top corner i think)

Either get the new winner a key or ask them to agree to deleting the giveaway. Re-rolling again and again won't resolve any issues.

No answer by support in 5 days.
My week was too stressful and I know I won't have time to check

support are volunteers, and they are probably as stressed as you are and also managing tickets here.

i don't think they can roll back to a previous winner unless they forward the ticket to the admin. wait for a reply.

you should have closed the ticket, but get another key has no sense at this point imho
however it's a shame this comunity has a so low numbered support
1 admin, 1 super mod, 4 moderators and 6 support little helpers, is that correct?
12 people to manage almost 1 milion users, good luck

I almost waited 6 days for my recent two re-roll tickets, even though some other of my re-roll tickets created around the same time for the same re-roll reason were processed much faster (only took like a few hours or so).

At this moment you could just get the winner a new key if you want to spend the extra cash, or explain the situation to the new winner and see if they agree to delete the giveaway.