Holding that the battle of Fort Sumter was the starting point of the war, the first shot fired immediately in the proximity of that battle can be traced not to the south but to the north. It was fired off the northern ship USS Harriet Lane on the night before the bombardment as a warning shot against a civilian vessle that was trying to enter Charleston harbor. The dispatch Harriet Lane along with a fleet containing other warships to Charleston was in fact the event that sparked the confederates to fire on the fort. They sought to preempt the fleet's arrival by taking the fort before it could act militarily against them.
and in every CSA's declaration of secession they cite the protection of African slavery as the prime reason for secession.
That is a half truth of history. Of all the confederate states and territories that seceded, there were four states and one Indian tribe that put out documents entitled Declarations of Causes. The four state documents did indeed cite slavery, as did the Indian tribe, though the latter was only in passing and cannot be called a prime reason in that document. The remainder either did not state causes, or stated causes other than slavery in their secession documents. There are 20 such documents that I have been able to identify, and they break down as follows:
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South Carolina - SO |
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South Carolina - DofC |
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Mississippi - SO |
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Mississippi - DofC |
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Florida - SO |
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Alabama - SO |
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Georgia - SO |
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Georgia - DofC |
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Louisiana - SO |
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Texas - SO |
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Texas - DofC |
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Virginia - SO |
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Arkansas - SO |
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North Carolina - SO |
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Tennessee - SO |
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Missouri - SO |
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Kentucky - SO [r] |
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Arizona - SO [t] |
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Cherokee - DofC |
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Choctaw et al - AofC |
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KEY:
Lincoln would have been content to merely limit the expansion of slavery into the terroritories.
That too is not so. Had Lincoln been fully contented by halting the expansion of slavery into the territories, he needed only to allow secession to procede. By leaving the union, the southern states gave up all affiliations with it including their common membership with and claim to the territories. If keeping slavery out of those territories was all that Lincoln wanted, he could have achieved it fully by not opposing secession and letting the south VOLUNTARILY end their claims to those same territories. But he did not and instead acted to halt secession, thereby indicating that his motive, whatever it may have been, was something other than the oft-stated desire to simply keep slavery out of the territories.
Alabama Secession Ordinance - it gives as a reason for rebellion the election of Lincoln who is "avowedly hostile to the domestic institutions" of the state. The domestic institution referred to is clearly slavery. What other institution could it be? So I believe that a 'Y' belongs in the 'Slavery as a Cause' section and the emphasis should be moderate.
Texas - their secession ordinanec contains the phrase "the power of the Federal Government is sought to be made a weapon with which to strike down the interests and property of the people of Texas, and her sister slave-holding States..." Again a clear reference to slaves. Emphasis should be heavy since it is the sole specific reason given, and is clearly the violations that the SO refers to.
Also you place the importance of the Secession Ordinances on the same level as the Declarations of the Causes of Secession. That isn't appropriate since the declaration of causes were meant to be the southern equivilent of the Declaration of Independence penned by Thomas Jefferson. These were their justification for their actions. Their record for posterity of the reasons for the causes which impelled the separation. As you admit defense of slavery, while not always the only reason, was the issue mentioned more often than any other. It was clearly by far the single, most important reason for the rebellion.
Finally, I believe that your final totals are a little misleading. A total of the reasons other than slavery given more emphasis than slavery would be useful. It would show, I believe, that compared to all other reasons, slavery was the cause mentioned more often and given more importance than any other reason.