DD-WRT is not designed for Malaysia use, ensure you have all the informations before proceeding so.

Also do take into considerations of the IPTV port (LAN 4), it's a VLAN port and shouldn't be tweaked. If you proceed then you will lost it since TM aren't going to release that information to you no matter how you begged them.

As for your firmware problems, you can try downgrade it to 7.05 before change it to DD-WRT, or you can always try performing the changes even at 7.13.

I suggest that you make a backup first of the firmware before any changes are done.