To disable firewall, you can just rename the /etc/init.d/S45firewall to something like K45firewall :



For samba filesharing, you can forward tcp port 139.

Beware that opening this port and running samba is not a very secure combination. I for one wouldnt trust the build-in security in samba if I opned it all to the internet.

You should consider mounting the smb share through a ssh tunnel instead, one page with some info on how to do it is here:
http://www.bitvise.com/file-sharing.html
or here:
http://www.blisstonia.com/eolson/notes/smboverssh.php

I've tryed your code but the firewall doesn't seem to be there

this is what I get

[admin@myasus root]$ mv  /etc/init.d/S45firewall  /etc/init.d/K45firewall
mv: unable to rename `/etc/init.d/S45firewall': No such file or directory
[admin@myasus root]$ cd /etc
[admin@myasus etc]$ ls
MACHINE.SID  group        ipkg.conf    ld.so.conf   profile      resolv.conf  services
TZ           hosts        ld.so.cache  passwd       protocols    rpc          smb.conf
[admin@myasus etc]$ cd /opt
[admin@myasus /opt]$ ls
bin         etc         lib         man         part2       share       var
doc         include     lost+found  part1       sbin        tmp
[admin@myasus /opt]$ cd /opt/etc
[admin@myasus etc]$ ls
init.d       ipkg.conf    nanorc       php.d        php.ini      samba        thttpd.conf
[admin@myasus etc]$ cd /opt/etc/init.d
[admin@myasus init.d]$ ls
S80thttpd   S97Samba    rc.unslung
[admin@myasus init.d]$

that is easy, with the  http browser enter in the firewall configuration page and disable it,
or in the console write the commands:
nvram set  fw_enable_x=0
nvram commit