rooting – remount, turn off SElinux, all fails even though I am root

I have a device which is never hacked into before, mostly as nobody has it, it is a android tv box. I have temp root using the dirty cow exploit, and tried to remount system using the mount command. it says permission denied even tho I am root. so can anybody guide me to get system remounted with rw permissions?

heres some of the shell:

$ adb shell
shell@ganesa:/ $ /data/local/tmp/dcow /data/local/tmp/run-as /system/bin/run-a>
dcow /data/local/tmp/run-as /system/bin/run-as
warning: new file size (9804) and destination file size (17920) differ
(*) size 17920(*) mmap 0xb6d64000(*) currently 0xb6d64000=464c457f(*) using /proc/self/mem method(*) madvise = 0xb6d64000 17920(*) madvise = 0 17449(*) /proc/self/mem 10931200 610(*) exploited 0 0xb6d64000=464c457f
shell@ganesa:/ $ /system/bin/run-as
uid /system/bin/run-as 2000
uid 0
0 u:r:runas:s0
context 0 u:r:shell:s0
shell@ganesa:/ # Hehehe
/system/bin/sh: Hehehe: not found
127|shell@ganesa:/ # which touch
/system/bin/touch
shell@ganesa:/ # touch Hi.txt
touch: 'Hi.txt': Read-only file system
1|shell@ganesa:/ # mount -o rw,remount /system
mount: Permission denied
255|shell@ganesa:/ # ls -ladZ sys
sys/    system/
255|shell@ganesa:/ # ls -ladZ system
drwxr-xr-x root     root              u:object_r:system_file:s0 system
shell@ganesa:/ # setenforce 0
setenforce: Couldn't set enforcing status to '0': Permission denied
1|shell@ganesa:/ # sestatus
/system/bin/sh: sestatus: not found
127|shell@ganesa:/ # cat
^C
130|shell@ganesa:/ #
130|shell@ganesa:/ #
130|shell@ganesa:/ #
130|shell@ganesa:/ #
130|shell@ganesa:/ #
130|shell@ganesa:/ # cat /etc/selinux/config
/system/bin/sh: cat: /etc/selinux/config: No such file or directory
1|shell@ganesa:/ # cd etc
shell@ganesa:/etc # ls
18p
NOTICE.html.gz
audio_effects.conf
audio_policy.conf
bluetooth
clatd.conf
dhcpcd
event-log-tags
fallback_fonts.xml
fonts.xml
gps.conf
hosts
media_codecs.xml
media_codecs_google_audio.xml
media_codecs_google_tv.xml
media_codecs_google_video.xml
media_codecs_performance.xml
media_profiles.xml
mkshrc
permissions
ppp
preloaded-classes
recovery-resource.dat
security
sysconfig
system_fonts.xml
wifi
shell@ganesa:/etc # touch lol
touch: 'lol': Read-only file system
1|shell@ganesa:/etc # mount -o rw,remount /
mount: Permission denied
255|shell@ganesa:/etc # su mount -o rw,remount /
/system/bin/sh: su: not found
127|shell@ganesa:/etc # sudo mount -o rw,remount /
/system/bin/sh: sudo: not found
127|shell@ganesa:/etc #
127|shell@ganesa:/etc #

I think it is SELinux, but even if I try to disable it I get permission denied. remember there is no access to recovery mode, nor bootloader nor usb adb. I have tried everything on the web

Thanks!