No, on a per user basis it's not a new record, not even close. See the point-timeline of Brian M. Scott around end of March this year for a recent loss an order of magnitude higher.
Yes, for 'large' accounts votes are often preserved. Actually the criterion are the votes cast, not the points of the user, considering both the absolute number as well as the number of users being affected. The precise threshold are not public to the best of my knowledge. See Don't throw away all votes when a user is deleted :
Sometimes the votes are also deleted if there are many. The point is that if there might be a problem related to the votes, then of course they should be discarded.
If, during review, it becomes apparent that the user is or ever was involved in voting fraud, the votes are discarded as they would normally be.
Now, I am given to understand that the implementation of this is very rigid. That is a minor irregularity in the distant past, will lead to complete invalidation.
I am pretty sure this is what happened, but per site moderators do not deal with such account deletions.