welcome!
i don't understand if you want to use HFS only to proxy the other service.
if that's it, than hfs is the wrong tool.
If you need HFS features, and also want to make your dvr public over the internet, given your DVR is a different machine than your HFS, then best solution is to configure your router to make the dvr directly accessible.
you'll have to choose a different port, if HFS is on port 80, the dvr should be on 88, or vice versa.
Other solutions should be held only as very last chance.