You are making errors in bash usage. If the location of the proftp binary is /usr/local/sbin/proftpd, you can't cd to /usr/local/sbin and then manually run proftpd by typing proftpd. You need to preface it with ./ So if you are in /usr/local/sbin/ the command to launch proftpd from there is
From anywhere else, all you need is the full patch, but launching executable files from the directory they are contained in requires the ./ before the file name.
The tab problem is that tab can only autocomplete for you to a non-unique digit. You say you have
procmail profiles proftpd protoize prove
all in the same directory, How is tab supposed to know with only pro typed in wether you want procmail or proftpd? You have to get to unique digits. If you typed prof then hit tab, the shell would see that it can't be procmail, profiles,protoize, or prove, and it would fill in the rest of the proftpd command for you.