Indeed, there were plenty of irregularities -- fraud and coercion -- in the secession process that people would still be arguing about today if the CSA had won.
Please avoid personal attacks. They simply convince others that you don't have actual winning arguments.
You have a double-standard on the legitimacy of puppet governments. MO and KY were both border states with split populations. Tell me, did the CSA also have puppet governments for NY and VT? No they didn't.
The fundamental point was that the secession of West Virginia was exactly the same issue of self-determination as the secession of the CSA. On the issue of self-determination alone, you cannot logically reject one and accept the other, nor accept one and reject the other. There must be other elements brought into the discussion to make a differentiation.
The fact that Lincoln readily accepted the concept of WV put the lie to the position that the North was fighting a war based on the position that former bonds were inseparable.
As for the abolitionists, they had a Holy War against slavery (not a bad thing to have a Holy War against). No, the priority was not war with the South, but they were certainly ready to go that route. The problem for them was that there was no popular support for it, which led to actions like John Brown's attempt at subversion. Even well into the war, freeing the slaves was not an effective motivator to get young northern men to die by the thousands.
Why did Lincoln and his supporters consider it worth war to make half the country, who overwhelmingly wished to split bonds, submit to federal control? That is the key question. If it was because they felt a moral imperative to end slavery, then that is understandable and at least defensible; however, this issue of preserving the union is highly questionable. If you have to kill and crush a state to make it submit to your union, it is obviously a one-sided benefit. Much the same as the difference between the union of marriage and rape.
Why did Lincoln reject negotiating with the the secessionist states? When half the population of a country which is ostensibly of, for, and by the people have a huge issue with the other half, negotiating would seem reasonable.
What would the South have wanted? Likely Constitutional assurances on slavery and an end to restrictions on slavery in the new territories. I think Lincoln suspected that if this was presented as the key to preserving the union, that most northern states would accept it, as an alternative to war. Lincoln wasn't going to allow that to happen.
Of course, the North could have proffered to have a national solution to slavery, say a 10-20 year plan to purchase, apprentice, and free slaves. That was a popular notion, and the cost certainly would have been less than the war. It was a common notion because it is exactly what the British had done. The South might have rejected it, but it would have been worth exploring.
So why not negotiate? Likely because Lincoln and his supporters saw a need to strike while the iron was hot, the country was agitated, and not risk losing a chance to end slavery, whatever the means. But that's not what he sold to the Northern people who would do the dying.
Thus, I return to my original point. The North fought to do a good thing (end slavery) under the false and flawed pretense of preserving the union, while the South fought to do a bad thing (keep/expand slavery) under the false, but morally correct, pretense of self-determination. Although other lesser issues did exist, slavery was the only issue that drove the South to secede and the North to make war.