I never could remove my 128 rc head from the centre column, I think after years of abuse in the field with salt water, spray, wear and bashing, it seemed to have corroded and fused together. This was after 15 years of head never being removed from the column.
I even let the engineers at work try to separate them to no avail.
I tried a socket deep inside the centre column to get to the head from underneath and in the end, gave up.
My only option was to buy a new head complete with a new centre column, only to find over the years that the column design had changed, going from round, to triangular and I believe also a hexagonal if I remember correctly?
This meant that I had to replace the tripod as well as the head
In despair I decided against the manfrotto as replacement opting for a gitzo which I certainly didn’t regret switching to.
I still remove the head on the gitzo every 6 months or so to prevent it happening again, and 2 years on all seems fine.
Good luck, maybe you could try ebay or somewhere selling an old tripod for spares, utilising the centre column and getting around it that way? But if you do, make sure that the head can separate or you will be in the same position again, also make sure that the column is the same shape as your original tripod.