I did define my practical limits. You decide for yourself what yours are.
1. of or concerned with the actual doing or use of something rather than with theory and ideas.
"there are two obvious practical applications of the research"
synonyms: empirical, hands-on, actual, active, applied, heuristic, experiential, evidence-based
2. so nearly the case that it can be regarded as so; virtual.
"it was a practical certainty that he would try to raise more money"
synonyms: virtual, effective, near
"a practical certainty"
I would say that any technical limit is well beyond the practical limit and the latter is for you to judge. I would not put a page of text into the custom sentence and a page is probably more than I would be comfortable with in the Note Editor.
Are there other descendants whose names are preceded by these letters?
I'm assuming there are and that the letters are just part of a numbering system for the report. In that case, it would seem that you have nameless people linked as children of some named person. It is more likely that you have parent-child links to a non-existent person.
Try running all the File > Database Tools and then look up the parents of these unnamed people and unlink them.