I can't see a connection between AdBlock and the number of port scans you get. But yes, you are safe. Norton is just doing its job and blocking them. Even if you got 100 scans a minute it wouldn't be a problem. If you want to prevent the scans from reaching you computer, you should consider getting a NAT router. That will block all unsolicited traffic and scans before it ever reaches your computer, and you'd never see a port scan in the Norton logs again.
Remember that it is highly unlikely that you are personally targetted. These scans are almost always bots scanning entire IP ranges, and you just happen to be in one.
It isn't in particular. Likely it is the same bot doing the scanning over and over for the last few days, and this is what you are seeing. No one said worms were intelligent. :)