Hmm. I compared your config to the one we use it's almost identical. Your right after reviewing the proftpd docs it looks like you just need to set AllowForeignAddress which you've done.
Is it possible that your firewall is still active or it's rejecting the connections due to some sort of configuration.
You might try limiting the PASV port range to narrow down the ports you need to make sure are opened.
Something like this
# Use to set range of passive ports to use
PassivePorts 6000 7000
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