I've tested both the dnsmasq and the FTLDNS version with unbound, no problems detected. For starters, I used the same wiki you did, but made a few small modifications (among others, there is a log file!), you can read it here. Just follow the unbound section, and of course, only 1 resolver in pihole's server configuration. You'll have to edit the files, this method doesn't work using pihole's web interface (different IP address).
By just adding the log file setting, you may be able to detect what is wrong.