Do you see any kind of problems on your end with connections from KNC (especially the hosting centre). Is there a "connection log" for my user that could tell you/me anything? As the miner is hosted, I have very little information from the hardware side; the only status I get is "pending" or "running"...
I don't know of any problems. If you leave me your Bitminter user name I can have a look in the logs. You are connecting to mint.bitminter.com on port 3333 ?
Would it be possible to adjust vardiff for different workers individually ?
Difficulty when using Stratum is per connection not per worker. Bitminter will choose a difficulty for the connection that is suitable for the fastest worker using the connection. That can be a little heavy for workers that are considerably slower.
Setting up two Stratum connections, for instance with Stratum proxy, should work. I'm not sure why you are experiencing problems with that. If you want the difficulty on the old proxy that you had already to drop then you may have to restart it.