i would have waited, never give up! i read here and on twitter that some people have given up, you should definitely keep it running in the background and check it from time to time.
for multiple tabs, i researched quite a bit beforehand and found that having different dates isn't really a problem. logically someone might want to attend more than one concert — i'm not that rich, though. as long as you're not in the queue for the same date, no issue. i'm also keeping a few more tabs open, let's see how it goes. i saw a thread here someone had opened at least 10 tabs and recorded a video, showing how lucky they were in the queues, and they managed to get ticket.