hello sir,
After I read the 3proxy's man page, I didn't find any options to limit the threads per minute for every IP, and also, we can't simply use iptable to do this limit, because for every connect IP, we should use a Hash Table to store how many threads it used in one minute, it's a little complex, so we can't use iptable.
but, after I checked the 3proxy's source code, I found it's written in C language, the good news is I am a professional Linux C programmer, so I have certainly confidence to modify the source code, and add this functionality.(then you can use it in configure file)
then you can delopy new version 3proxy on your Linux or Windows server, and update your configure file.