I think it's great but since it's a gag manga revolving round a single premise, I can't see it being really long. Maybe 1 volume?

While you're probably right (Tamamusi hasn't ever done anything longer than one volume anyway), it's definitely possible to draw out a single gimmick for a pretty long time if you're creative about it (Tonari no Seki-kun for example is going on volume 10). I'm sure there are enough "one-sided firsts" to explore to get this to three or four volumes at least, if the author is interested in taking it that far.

Just wanted to point out that the handedness thing isn't a plot hole, it was a mistranslation in that other chapter. It wasn't "If Hinoko was ambidextrous...", it was "I thought Hinoko was ambidextrous...", and the "Ah!" moment was her realizing that Hinoko was pretending to have trouble so that she'd feed her.