I sent 4 bitcoin and pay only $0.08 fee. It depends on the transaction size and age of the coin. I do use my own full node.
It doesn't matter that you're using your own node though. There's still a decent amount of nodes that both receive and relay low fee transactions. This policy changes a bit in 0.13.0 as the nodes will share minrelayfee information, e.g. node A won't relay transactions to Node B which node B wouldn't relay anyways (this is a waste of bandwidth).
can the confirmation be done by one node only?
No. Confirmations have nothing to do with nodes. Confirmations are related to mined blocks; nodes are used for relaying TX's and blocks.
how this can do against sybil attach? i thought that there were the need of multiple node to verify the ttransaction and confirm it
No. Read this book:
Bitcoin For Dummies.
If you want to use premium wallets like blockchain you have to give them good fees.
No. Blockchain.info is not a premium wallet; it's just a web wallet. Those should be generally avoided.