Looking at their standings they seem friendly with Caldari 4.0 one way and 6.0 the other way. Shouldn’t this mean that if I do a Storyline for them my Caldari standing would also increase a bit?
Just did one and nothing positive or negative happened to my Caldari standings.
The derived standings will not exceed the “default” standings between the factions. At some point the Caldari will treat you like any other Ammatar citizen, meaning you cannot exceed a base standing of 4.0 with Caldari by doing storyline missions for Ammatar.
The same is true for the lower end of standings. Your base standings towards Minmatar will not go below -3.0 that way. But it’s always possible to go lower by taking direct actions against a faction, like killing their ships.