Well you've caught a few more Shinies since, haven't you? Great job, it's exactly how it happened for me - I kept trying and trying without success, and then after I got my first Shiny, they kept reeling in ^^'
Yeah, they are, but you'll probably have to get used to them breaking at those stages. I've had my fair share too :/
I tend to have good success when i'm not even trying to get a Shiny from the chain, even with the rare Pokés, but it's odd how you can chain a hard to find Pokémon easily, and have difficulties with a common one. It's so random at times ._.
Hmm, I haven't chained for over a month. My latest Shinies were the Drifloon, Cherubi and also a Spiritomb, from SRing(yeah, they came really quick - all within 16 days =O). I will chain again, i'm on the verge of restarting Diamond, but i'm just waiting to see if a friend here wanted any of my leftover Synchers/Radar Shinies or not beforehand.
Pearl's boxes are still too full to chain anything x_x