1) is there at all the possibility that the transaction will eventually be confirmed?
Yep. Every miner decides for himself whether he will include your transaction in the block or not. And since its priority rises over time (see
https://en.bitcoin.it/wiki/Transaction_fees#Technical_info), and your transaction is considered "standard", over time it's more and more probable for it to be included in a block.
2) in the meanwhile, that tiny btc amount is someway freezed? Am I able to spend them again (i.e. to use them from the same "unspent output" I picked them in order to build a new transaction)? Or they already belong to the new address and I will be able to spend them only from that new address and only if and when the transaction will be confirmed?
Not until some time has passed and nodes drop it out from their memory pools. Otherwise they won't accept another transaction that spends the same outputs and they will not relay it further. You can of course try until it succeeds.
3) does the transaction priority would have changed, even minimally, if I had included a 1 satoshi fee in the transaction? or the amount of fees is not important until they don't reach the "suggested" value?
Nope. If you pay a less than recommended fee, it is generally considered by miners as if you would pay no fee at all.