I've got an Issue and a question

I've got two things. I have an old Netgear WNDR3700v1 that ultimately became a hand me down in my direction. I immediately installed OpenWRT on it to some success and some issue.

The Issue if I try to say stream a 4k file through the network or play a game through steam link that's a big resolution the router will keep on trucking and the WIFI will function but the the ethernet ports will cut off effectively removing access to my pc unless I unplug / replug the cable into the router.

Second is the question. I'm trying to set this up as an internetless lan / wlan that I'd like to function with Batman or Cjdns as i'm a supporter of Mesh Networking / decentralized internet (Yes I realize no one will connect anytime soon but It's still something i'd like to do,) Is there a recommended setup for something like that? And is there a way to make my devices think there's an "Internet" If I setup Batman or Cjdns?

Version installed?

OpenWrt 18.06.5 r7897-9d401013fc (I'm assuming this is old?)

Depends what hardware you are running

I literally said it in my post Netgear WNDR3700 v1

Yes, after you edited your post

Reading his edit the device was still in the main post.