Regarding the supposed change from teh OT — I don’t think he did change from vengeful to compassionate. I think he was teh same throughout and that perception is solely an issue of the perspective and writing style of the authors.

Regarding Christ succoring his people — the HCK/MMP model has a built in answer to that. Some feel He went through basically all the trials and pains of humanity prior to his role here in that model and as such could very literally understand what it is like (especially assuming the veil of forgetfulness was lifted for him.) But in any model the scriptures at hand seem to only be saying that he understood what mortality was like because he went through it here. And besides “the Spirit knoweth all things” to fill in the experiences he didn’t have.

What about the fact that He, Christ, still would have had to take upon Him all the pain and suffering to succor those who needed it as I said above and also so he could mature from the Vengeful OT Jehovah into the Resurrected Christ, full of mercy.

This was his last step for His progression to become like His Father.

I was reading the Ensign and thought that maybe the brethren were going to answer the question for me, they got close but no bubble gum cigar.

President Faust spoke of Spiritual Healing and spoke of Christ as the Comforter and Healer as I did but he never went so far as to say that saying that although we will still have pain we can be comforted by His grace and mercy

After full repentance, the formula is wonderfully simple. Indeed, the Lord has given it to us in these words: “Will ye not now return unto me, and repent of your sins, and be converted, that I may heal you?” 18 In so doing, we have His promise that “He healeth the broken in heart, and bindeth up their wounds.”

We find solace in Christ through the agency of the Comforter, and the Savior extends this invitation to us: “Come unto me, all ye that labour and are heavy laden, and I will give you rest.” 19 The Apostle Peter speaks of “casting all your care upon him; for he careth for you.” 20 As we do this, healing takes place, just as the Lord promised through the prophet Jeremiah when He said: “I will turn their mourning into joy, and will comfort them, and make them rejoice from their sorrow. . . . I have satiated the weary soul, and I have replenished every sorrowful soul.” 21

And in the celestial glory, we are told that “God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain.” 22 Then faith and hope will replace heartache, disappointment, torment, anguish, and despair, and the Lord will give us strength, as Mormon says, that we “should suffer no manner of afflictions, save it were swallowed up in the joy of Christ.” 23

This however does not really say that he took upon Him all the sickness. But It does say that He will comfort us. As for healings, I have seen the priesthood work to many times to argue that point. God Heals when it is within the will of His plan of progression. That may sound trite, but I have seen it.
I have a good friend who is in complete remission from cancer while I have seen many, many people die in my career in the hospital. Death and pain are a part of the plan. How we comfort each other (eg:Mosiah 18) is also part of that test. I have learned that treating a terminal patient with respect as they pass into the next life is vital to my progression.
What does that have to do with what the Atonement covers, well, again, It covers sin, and it covers children, and those without the law,and it allowed Christ to Descend below them all and mature from the Vengeful, premortal, OT Elder Brother he was to the Merciful, Post mortal, Resurrected, Bowels full of mercy, Christ who succors his people as they go through their trials and waits to bless them if they will just ask.

That is the assumption I am questioning here. Where does it say that besides Alma 7? I think that such a reading of those comments by Alma is a stretch.

It never states that we would never suffer but that He would comfort us. There is an inherant pain in growth that must be paid an therefore to take it away robs us of that growth, but to have someone who has “decended below them all” with us to help us back and to comfort us on our journey. That is the fulness of the Atonement, at least to me.