Pleased you made headway with your search in London though none of the dates you mention tallies with any of the dates from my record. If you contact me by my email, [email protected]
I could email you all my dates so we narrow down the period I actually sailed with your dad.
The stevedores? Some retired I suppose, but some went to work at sites where cargo was loaded into containers for both road and sea (I recall one of the first sites at Garston) and other stevedores went to work at the container docks, such as your own Seaforth and Ellesmere Port and most ended up (allegedly) on rates of pay that made them millionaires compared to us seafarers due to the way their salaries were structured.
From Liverpool we carried very mixed cargoes, bits and pieces of everything from agricultural tractors to toilet bowls (one voyage we took pedigree pigs to Lisbon for pig breeding), The textile industry was a booming industry in Portugal at this time and we carried lots of industrial knitting/weaving machines, nylon yarns, polyester pellets for nylon type clothes etc. We also carried whisky, cornflakes, HP sauce and every other commodity.
Coming home from Portugal the cargoes were sometimes port wine and Mateus Rose (as you say) - (100s and 100s of tons of Mateus - no idea where they got all the grapes!) but we also carried lots of cork in bales and also granulated cork in sacks, they don't weigh much but they certainly very quickly filled the holds. We also carried big rolls of wood pulp paper and barrels of cork sap (called rosin), all stuff you'd expect from an agricultural country.
Hope all this helps to paint a picture of your dad's career. I find it surprising there are no other ex-Ellerman personnel on the S.N. site who remember your dad