I added the conf file and that didn't work either.
I seems the best solution would be to re-sync completely. My blk0001.dat file size is around 1,154 Mb, so much less than yours, and though I still use version 1.5.1.1, it syncs well (though took a while to re-sync for the last few months), and stakes perfectly. I could provide a blockchain snapshot if you would like one.
That could take awhile, on my experience. The wallet used to sync about 500 blocks, then wait for quite some time, then sync further. Overall syncing for 4-5 months took more than 24 hours due to that. At least the CPU usage was reasonable, so I believe its not the reason of this behavior.
