Hi!
1. The colors in the block layout are inherited from the theme, but you can change the text colors by using this custom CSS.
.asp_option_label {
color: red !important;
}..and for the legend header:
.asp_sb legend {
color: blue !important;
}2. To force it to the center, use this custom CSS, it should do the trick:
.asp_sb form.asp-fss-column {
text-align: center !important;
}3. In this case, try changing the checkbox logic as following: https://i.imgur.com/t0HtcMb.png
You can also try the other option value, to see which one gives you the best expected results.
I will make sure to re-test the plugin back-end on RTL layout to make it much easier to configure, thank you very much for letting me know.