Hello Alexey,
actually I have seen you are also contributor for the cs-cart boilerplate theme.
Let me give some points for your request in the first post.
First of all it is a pleasure to see that cscart finally had made the step to a bootstrap theme. I remember me having given this idea to the cscart team by the bugtracker as idea about ~2 years ago. One big issue cscart has is its lack of available Themes. Themeforest for example has a ton of other shopping software themes, but for cscart it really looks bad. This situation is still in place. So a logic way to solve this is giving a theme to the community which is easy to use and can make use of allready available Themes / Snipets, like bootstrap.
Regarding the questions:
1. We clone the theme, and try to use hooks > tpl files for chcanges. (we try to make as less changes as possible so they still can work with updates)
2. By hooks including our custom .less or .js
3. Fonts: design/themes/{theme}/media/fonts/addons/*, for Images we would prefer the design/themes/{theme}/media/images/addons folder, however cscart sometimes does not give support for it, like the php fn_generate_thumbnail function, which requires a path in maindir/images.
4. Think so
5. We search the templates for the css classes shown in the html code. However this is SSH based, so this is more of a non-common way people will do it or being able to do.
6. product_data.tpl: I am actually looking into product_data.tpl again for redesigning the Product Page. Here is my thought: I really would wish I could use the Drag & Drop Editor for changing the Structure of the Product Page. Block for the img, different price titles, buttons & Tabs Area. Its much more intuitive and developer friendly. Maybe thats only for me but I really like the Drag & Drop system - so why not using it also for positioning of that sub-elements. Same goes for Category Pages.
7. No
8. We do not use it often, only for php/mysql debug stuff, but its rare.
9. No, they are very usefull
10. Not sure on this
11. We create a new theme so it is stored in the default Demo Theme.
12. Please refer to #6, We would love to see blocks available for designing category Page and product Page. Another huge plus would be the support for more dynamic grids like 24 or 32 Grid. The 12 and 16 Grids have some disadvantages regarding spaces between elements. Sometimes you want 1/3 1/3 1/3 which only works for the 12grid, but than you also want some kind of splitment which only works for the 16grid.
13. Yes we create custom. We would wish more flexibility for the Color Selector, like transparency.
14. We prefer hooks ofer tpl changes.
15. If using a custom schema.json, the new variables are required to have been set in theme editor before putting them in less file, otherwise throws error because they have no value yet.
Kind regards