Britain forced a treaty under threat of war imposing a partitioned Ireland - sign in three days or it's war'

No it did not, and the treaty you refer to was rejected by the Cabinet and then by the Dail anyway.

At that time, partition was already agreed.
Part of the treaty was about setting up a boundary commission to decide the border.
None of it was about imposing a partition, or anything else to do with partition.

The civil war was an entirely Irish thing.
Britain is not really to blame for all Ireland's problems Jim.