I've had my Saga for a month now and the finsh is awefull the first time I moved the safety down it removed the finsh and now there's a big sliver line.
Every AK ever, anywhere, has that line. It wouldn't matter
what the finish was (well, maybe hard chromed) that line is going to get scratched through the first few times you move the safety/selector lever.
When I Duracoated my -74S, as soon as it was dry I ran the safety 5-10 times to get the line etched back in so it wouldn't hang or snag in the paint.
I've put 100 rounds throught this gun all Ulyanovsk 7.62x39mm and i've had 5 jams all on the first shoot. I know this is cheap ammo and it's steel case but it's all my wal-mart has. Does this gun shoot better with brass cases such as golden bear?
Unlikely. Sounds like a magazine issue to me. (If it is doing this with multiple mags, it's probably that the mag catch isn't holding the mag level or high enough.) An AK should feed anything, always, ever. Most AKs in the world will never see a brass case as the military issue ammo is all steel-cased.
If it isn't feeding I'd think you have two options. Complete the conversion (back) to AK pattern so you can use normal AK magazines. If done well, this will almost certainly fix whatever alignment issues the current Saiga mags are showing. Or, send it back to the importer and have them fix or replace it.
Wondering if should Dura coat this rifle since the finsh seems to offer no protection.
Duracoat is o.k. As are the good paints like Alymahyde, Cerakote, etc. Heck, a good high-temp Krylon rattle-can paint will do just fine if you prep the metal right, and it's cheap to touch-up.
But, none of those is going to provide more than a little bit more protection than the factory finish. Might be a little more resistant to solvents/oils ... might not be. Not going to hold up a whole lot better to wear, and, again, none of them will stop the safety lever scratch line.
If you do the old military trick of parkerizing first and then painting over that, it will be about twice as durable as the park really grips the paint.
If you really wanted a super-durable finish, you could sent it to someone to do a hard-chrome finish, but that's going to be probably over half the price of the gun.