Hi Marco,
First of all, you are correct that the wlconf application you should use is located in /usr/sbin/wlconf/
The correct location of placing the wl18xx-conf.bin should be under /lib/firmware/ti-connectivity/
It looks like your wl18xx-conf.bin is either not generated or not "properly" generated. Do you see this file under /lib/firmware/ti-connectivity/?
And can you provide the commands you entered when generating the wl18xx-conf.bin? If the wiki page is correct, you should be able to successfully generate the file.