I caught the shiny Cobalion and want to thank everyone that has helped make it possible!
To contribute to the forum I'll leave some advice for people RNGing stationary Pokemon who happen to read this.
If you RNG for a shiny Poke and can only find high shiny frames, 300<frame, include multiple key presses in your searches to broaden the results. Having a low shiny frame makes the whole process so much simpler.
If you find that you struggle with synchronizing your console's clock with an external clock, and are not sure how many seconds to start the game to hit the seed's date, do the following: use the recommended starting correction (eg. 7-8 seconds for the 3DS, but make sure you stay constant with your time) and catch the Poke. Write down the poke's nature and IVs (you will have to find a way to find the exact IVs, I used my action replay and Serebii's IV calculator, using the action replay to get a lot of rare candies and leveling the Poke then plugging their stats and nature in the Serebii IV calculator). Repeat the process multiple times until you begin to catch multiple Pokes with the same IVs. For the Pokes you catch the most plug there natures and stats into your RNG reporters time finder and find the seed that matches the date of the seed you want to hit. Look at the seconds, if the second is a second higher than the date of the seed you want to hit then make the correction time a second shorter and etc. This way you can feel comfortable about the time you begin your game.
To calculate the frame correction due to wondering npcs, pick an estimate number to advance the frames and catch the poke (this is why you want a low frame, it really does make the process easier) until you land on your seed and take special note of the Poke's nature (again you can check the Poke matches the seed's IVs by Serebii's iv calculator, it should be obvious when Serebii matches the seed's spread even without the action replay). Use the RNG reporter screen that shows each frame and its Chatot pitch and see if you can find the nature closest to the frame you need to hit. If there are many frames with the matching nature see if you can decrease or increase the number of you estimate frame advancements to hit a nature that is unique. If you can hit that unique nature then you should safely be able to see how you need to change the estimate frame advancements to hit the frame you need to hit.
Good luck!
