Well, the game has a broken PRNG, meaning that if you hit A before that location bar drops down, it won't load any new Numbers, so if you have a shiny number in those 200, then you have a 1/200 Chance of it being shiny. If you go around 200 resets, and it isn't shiny, you'll have to start a new game (I am also wondering if just waiting for the new Numbers and then saving after you get them may work)
Not a very accurate description of what's going on. There are no "groups of 200 numbers"; just a long, continuous stream of numbers, which on Emerald, are always the same ones for a given number of seconds since the game has been turned on/SRed. The aspect which you're right about is that SRing shinies is either going to be very easy or nearly impossible for you on an Emerald game.
Also, because some targets take longer to SR than others, you will be drawing from different sets of numbers for different targets. E.G. Kyogre/Groudon must take the time to crawl out of their craters before they battle you, taking some time, whereas the Regis are nearly instant. Fufu, that's probably why you're not getting your Regis. You'd probably need to wait around 3 seconds before talking to the Regi if you want it to shine.
I'd advise against even trying to SR for anything on Emerald. The odds are slim that you're going to have a lucky game, and the only way to really find out is to get a shiny.
Personal status: That Chikorita I hatched isn't quite as amazing as I had hoped. Her IVs are 31/12/31/24/31/8. Triple flawless in the defensive stats, but the Speed could be much better, and the Special Attack isn't outstanding either. (Attack doesn't matter one bit, but it's bad as well.) Still, this is much better than my previous female breeder, so I took her through the Gardevoir base and dropped her into the Daycare. I also tutored Counter back onto my male. Luckily, I had a L75 clone kicking around, so that's the one I put Counter onto, so I can also evolve him, EV him, and give him a competitive set. I might bring my old breeder, who hit L100 in the daycare long ago, into D/P to see if I can score anything off the GTS with him. Mainly one of those stupid "no one sane is going to have a L100 [insert unevolved Pokémon name here]" requests. (Or if you want to make me an offer, go right ahead. :classic:)