I've set Port 1909 to diff 1000 - so if you have a ASIC/Zeus etc. try this Port :
stratum+tcp://cam.suprnova.cc:1909
Would be interesting to see if that lowers rejects/invalids now
on port 1908 ...

on port 1909 ...

Ok so this actually looks quite good. Fine.
Concerning the nicehash "difficulty too low" that usually means Nicehash cannot connect to the pool, i'll try to contact nicehash as they are having other issues as well.