Hearthpwn

Thalnos --> Kobold Geomancer

Black Knight --> Spellbreaker or possibly assassinate

I can't really say. It depends on what classes are dominant in your current rank. I found that higher ranks tend to have more hunters and zoo warlocks which this deck might not do very well against. My guess would be ~rank 10, then switch to an aggro or control deck. Personally, I made it to rank 10 with a similar deck, but I could not go any farther