I generally think you're connection might be having some issues itself.
The sites downloads are all fine as long as you got a solid connection yourself.
If there's missing things such as folders and markings etc, I'd actually suggest you to uninstall the game completely, removing the FH folder from the C:\ drive as well. Once that's done, download both the game installer and the newest patch from our download page again (best if you used utorrent and a torrent download to ensure you get working ones and not the same issue again).
Install the game, and it should work better that way.
However, FH shouldn't slow down your internet down that much when playing unless you already are using your bandwidth for other things. There might have been some changes if you've been away for months, cause FH has around 100 more players just around peak times now.
First fix the game itself, download a fresh copy and uninstall the old one since you clearly got broken installers the last time, and use torrent.
Once you got a working game again, see if it made any difference, if not, make sure your connection is alright, and no other devices and programs are using your bandwidth preventing you from connecting to the game.