I've read the TzScan.io API documentation, but could not find an endpoint that allowed me to get a list of the transactions of an specific address. Considering that TzScan.io has already a transaction TAB functionality, this might exist. So how can I get a list of the transactions ever made by a tz1 address?
You can use the operations endpoint, filtering for transactions:
Obviously swap address for the address in question. You can retreive the amount, destination, source, fee, gas limit, storage limit, if the tx was internal and also if the tx failed or not.