Now you know why there is a split feature in SB. Split the list a bit. Don't be silly and try to work with million url lists.
If it's the list that has been floating around for about a year 90% of it is junk now anyways. If you really used a link checker I bet less than 1% actually posted. Average success rate is between 1 and 2% with those lists. Also the ones that posted probably have 3,000 OBLs so the link has no weight or negative weight. It is just a waste of time and resources to work with those old huge lists.
As far as 300,000 posting, no way. Because SB says it had success doesn't mean the link posted. Do some link checking against that 300,000 and I bet you don't find 3,000 with your anchor text and link showing.
There is a lot more to SB then finding or buying lists and spraying away.