1) I not sure what you mean when you said "Pedia and UI". The UI already contains Pedia and WB. Anyway, if you pressed the valid civics (white), the right columns will show the comparison, as well as list of changes in Change Column (Screenshot 1).
Even if you pressed an invalid civics (red), nothing will show in Change Column, but you can still compare. (SS 2)
If you hover over the civics in left table, they should have the hover text like in a Pedia. If you don't get hover text, that means it is not working, such as interference with BUG which disables the python hover text. Or C2C which has their own way of writing hover text. Check how it works in the standalone UI itself, and compare with your mod.
1b) All items which can be customized are in the customization section of the PediaMain File. Set bLeft to True. For now, I don't intend to make it like BUG to save changes and write it into a file, because I am lazy
2) The icons on the left cannot change because they are using tables, where the code to adjust row height doesn't work, so no point having bigger icons.