Regarding Kabbalah:
Whether or not it is a deviation from the mesorah and, therefore, wrong, is irrelevant. Lihavdil, Christianity is a contradiction to our ikrei emunah.
yitayningwut, no, the concept is not there in the gemara Sukkah either. There is no source for a person’s anything atoning for all mankind.
(First of all, it would be ridiculous to have the many halachos of korbanos, teshuva, kapparah, etc. if there were no need for any of that. So the gemara obviously cannot mean what you imply.)
I wish to leave this to the talmidei chachamim to address.
However, from a very quick glance at the Maharsha, whatever the gemara does mean, that gemara has nothing at all to do with the Christian belief you are implying it parallels.
The Maharsha mentions, for example, that during the entire time Rav Elazar had his yissurim CH”V, that nobody died before his time. It does not say they lived free of sin nor that they bore no other punishments CH”V. And that particular immunity ended when his yissurim did.
And nowhere does it say he meant there is no more sichar viOnesh, etc. ch”V.
(While you’re at it, you can also say that since Hashem commanded Avraham Avinu to bring Yitzchak at the Akeidah that this CH”V condones human sacrifice. Of course, the truth is the oppposite that this was a mind-blowing test that they both passed with flying colors to our tremendous merit forever.)
As I said earlier, you can twist anything to mean anything, but not if you’re objective, honest and educated. Bringing this gemara as a source for their belief is none of the above.