My apologies here.
If you would have mentioned satellite internet in your original post, I would not have been so far off course on my suggestions to help you, which was my fault. So, I am sorry for leading you down the wrong road. Hopefully, some of this has at least checked off things not applicable.
You have to know about
satellite latency, yes?
That is the most likely reason for your connection issues. Your home network looks to be in order.
Aside from that, it looks like you have everything compartmentalized well and a good registry cleaning would not hurt.
As for you not having a "AppConfigLocal.xml", it occurred to me that since your install is Steam, you can "Verify Files" to see if it is one that the game sees as missing, and downloads one for you. As a test, I renamed my copies and ran the game. They were not recreated, but the game ran fine without them. So, aside from turning on IPv6, the game does not seem to need it. None the less, reverify your game files and see if it appears. It's a handy file to have for playing with UPnP, IPv6, Portforwarding.
EDIT: VPN over a satellite connection will slow your internet speed. Use the same speed test above with and without VPN to see this. I turn off VPN when playing Elite as my upload/download speeds are a good one-third faster. The game does not need the security of VPN, although it will play through it.
EDIT: It would be well worth the effort to get your IPv6 working on the router and in the game, as two IP Stacks are better than one. If you run IPv6, it will go around the VPN tunnel. All IPv4 connections will go through the VPN tunnel. IPv6 connections will not. So, you mentioned your router supports VPN. If you have to turn it on or off inside the router and want to leave it on for security, Elite will use IPv6 to go around the VPN tunnel. With VPN off, IPv4 and IPv6 will be available for Elite.
Good luck.