As for your seeing that the large head disappeared, one of the kings shall die in his bed, but in agonies: See 2 Esd 11.33. The problem noted in Revised Standard Version‘s footnote here involves a translational matter, so it is not needed. Good News Bible provides a good model for this verse, and so does Contemporary English Version, which says:

• You saw the largest head suddenly disappear. That’s because one of the kings will die a painful death while sleeping.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Esdras. (UBS Helps for Translators). Miami: UBS, 2019. For this and other handbooks for translators see here.