Hello @Stob and thanks for your answer! 
I also have realized that the node is outdated, there is an issue with the updater link.
Incorrect. You don’t need 1 ETH as a minimum, it just needs to be enough to cover the transaction fee. Also zksync transaction fees can be paid in STORJ instead of ETH.
I will try again to buy less than 1 ETH on MEW and see if they allow me to. Another option could be to transfer ETH from another account which allows me to buy less than 1ETH. Still it is not an easy process I find, because each step requires fees and those are not that easy to calculate in advance.