I can't imagine he would apologize for "being short" (of stature) unless you made some comment regarding it initially......I presume he thought he was being "short" in the 'rude' sense of the word with his replies to you and wanted to clarify that......
based only on your comments in your first post, I think you may be making an inaccurate leap of judgement about Ben's mental 'stability'.......it's entirely possible he's had a hectic week and is not at all focused on replying to indefinite RM inquiries like yours at this point.......
Ben has a fine reputation and lots of regulars......as suggested above, it's usually best to quickly get to specific date-and-time planning.....I'd wait a few more days, then message him with a brief note hoping things are cooled down for him and asking if he's available at xxpm on xx date for xx hours at (insert location here)........as always, be polite, professional, to-the-point, and discreet......
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