Why can't I load Steam's verification code after using a proxy, but if I don't use a proxy, or use a Russian IP he can display the verification code normally, I am confused about this.
Export your spreadsheet as csv file, than import it to BAS as a resource and set it to use each line 1 time (it is default setting I think). That way each thread would take new line from your csv file in run mode or as compiled bot.