3. The number of sun is 6. If the Pleades are regarded as a constellation with 6 stars, and if they announce a soon to come solstice (maybe both solstices), then, in order for the double maitaki sign to represent Tauono, there should be 6 'stones':

The vertical line through maitaki could mean that each 'stone' is a double-month. A regular solar year has 6 * 60 = 360 days.

Another possibility is that the vertical line has at left 3 sequential periods and at right another sequence of 3 periods, i.e. 6 periods which are ordered by the string rather than by the 'stones'. This possibility may have been used in e.g. Ka4-8, where the 'stones' at left appear to be different from those at right:

The 'stones' presumably represent two periods, but we can only see half of each such period, represented by a semicircle. Such semicircles appear in other glyph types too, for instance at the top respectively the back of the head in Aa7-8 and Aa7-11: