Firstly SuSE is a bit different and the tutorial may only be mostly correct, if it doesn't note the differences that are specific to SuSE.
Secondly, you don't seem to be restoring the ruleset, so you shouldn't be surprised that the ruleset doesn't get restored.
To the first point, by default SuSE uses its own system for configuring the firewall and that involves an 'early' block-anything-not-needed-for-boot stage and then a more precisely configured late stage. You could be tripping over either of these stages, so you need to check from the run level editor in yast that this isn't going to be the case. (This also raises the question why you aren't going with the flow and using the SuSE firewall system, but that is, of course, up to you. If you do change your mind, configure from YAST.)
as a search on google indicated that the file format might be incorrect otherwise. After a reboot iptables was back to the open state.
The firewall is only persistent if you make it so, in other words, if you restore. The iptables-save/iptables-restore system does have advantages if you need to preserve counters across reboots, which is difficult to do otherwise. OTOH, if you aren't interested in the counters, this isn't really an advantage.
To do it this way, you need to use iptable-save to dump the contents to a file and iptables-restore to put things back in place - you'll need the -c switch to do the counter thing. So, somewhere in the boot process, you need to execute a script that does this, either get the YAST runlevel editor to do it, or run a trivial script from the appropriate /etc/rc.
There is usually good documentation on networking, etc, in
- the SuSE books
- the SuSE website
but its sometimes a bit difficult to find what you want if you don't have the books.