The -k argument on my openssl accepts a passphrase, not a file. You likely encrypted with the filename as the secret, not it's contents. Perhaps you should use -kfile instead.
$ openssl aes-256-cbc -help
Usage: aes-256-cbc [options]
General options:
-help Display this summary
-list List ciphers
-ciphers Alias for -list
-e Encrypt
-d Decrypt
-p Print the iv/key
-P Print the iv/key and exit
-engine val Use engine, possibly a hardware device
Input options:
-in infile Input file
** -k val Passphrase**
-kfile infile Read passphrase from file
You mentioned ping. If you're using Termux you may need to manually update its DNS settings (different from the system DNS). The file is /data/data/com.termux/files/usr/etc/resolv.conf
To make it roam you probably want your home dns first then some internet resolvers after that.