First, present table styles are not styles in the usual sense but rather templates.
What I mean with this statement is best illustrated by an example.
Paragraphs are formatted according to paragraph styles. Provided you don’t override formatting attributes, modifying the style will be immediately reflected in all paragraphs depending on the style. Similarly, if you assign another style to the paragraph, the paragraph is reformatted automatically to the new style definition.
None of this is possible with the so-called table “styles”. Once a table is created, it loses any association with its original “style”.
This is exactly what happens with text in a template (I put aside the styles definitions in a template because they interact nicely with the style dictionary). A template file may contain initial text which is used when instantioating a new document. But if you modify afterwards the text in the template (once again, I don’t complain about the styles), this text change is not forwarded in the derived document for two main reasons: 1) there is no explicit backlink between the text and the template, 2) you may have customised the text and it would be very user-unfriendly to change your intentional prose.
Definig a true table style, i.e. a named set of attributes for
Table Properties would be a very valuable feature. However, experts told me this is presently not included in the ODF standard. If you have the skills and competences to implement a prototype, this would be a first step towards adoption.
Consequently, for question 1, 2 and 3, the answers are “no”.
For question 4, remember that pixels on screen have a fixed size. What is displayed has an integral multiple of pixels. For very tiny objects, like your 0.05pt line, either it is considered too small and is simply not drawn, or it is considered an “important” element in your document and is drawn at the smallest screen size, i.e. 1 pixel which is frequently 1-96" today (was 1/72" in the past, not to speak of recent HDPI screens)).
Question 5: I don’t know how the table “styles” are implemented, but they may be as some sort of macro. This could explain why you can’t create new templates (contextual menu only shows
Hide in the side style pane).
Question 6: this is a matter of personal choice. Due to the limitations of this template feature, I prefer to avoid it but YMMV.