This depends on the filtering rules that nodes use.
Let it be full and see what happens 
Nothing. If the transactions are indeed spam, then transactions with proper fees and adequate priority will process just fine. I just want to see the effect of a rising min relay fee. How expensive is enough to stop people from using bitcoin? For rich people moves thousands of coins, even 1 btc fee is nothing, so they will not be affected. If average people is moving 0.1 btc, then 0.001 btc would still be ok (1% fee), that's still almost 10x higher than current fee