And a bigger fish!

3 TH/s is really serious gear!
I'd say, as an unrequested advice, that with 3 TH/s you can use a much higher difficulty than 256.
I'd try with 2048 at least, lowering your fee to a little less than 0.3%
spiccioli
if the pool goes wrong, with --disable-rejecting, the issue could be solved faster with a lower diff.