Owning slaves isn't actionable worth at the time

I don't know what you mean by that, could you perhaps explain it a little bit?

They lost the election by a split vote. Purely northern states wanted to impose their will on southern states.

They still lost the election. Sucks to suck, welcome to democracy. And the Southern states wanted to impose their will on Northern states too, by forcing northern states to return runaway slaves, etc.

They fired first because they were idiots

Without a doubt.

The seceded because they objected to having no say and no rights in their own territory.

You have no right to declare your state independent because you lost an election, and you especially have no right to declare your independence in order to preserve or establish slavery, which is expressly why they seceded.

They seceded because they were afraid the North would ban the immoral practice of slavery upon which their economy was based. The South had been wielding great power in the legislature for years because of the 3/5ths compromise.

By expand you mean establish more states with westward expansion? The North imposed their will on the south which completely violated the basic compact of the union in the first place.

Considering that the South had been imposing its will on the North through the 3/5th compromise and Dred Scott Decision, that's a real case of the pot calling the kettle black. Furthermore, the Fugitive Slave Act of 1850 can be seen as forcing citizens to take part in the immoral slave trade, by imposing fines and imprisonment on those who assisted runaway slaves.

And of course they would want them returned, they were property to them. This would be like crossing a state line and getting your car impounded then sold off because someone else didn't like that you owned it and you got nothing for it.

No, it's more like crossing a state line with a slave and having them freed with absolutely no recompense to you because slavery is a horrifically immoral act and you deserve nothing but jail time for it.

Both sides were dicks to each other.

Tu quoque. The South fought expressly to preserve the institution of slavery. That makes them the bigger assholes.