I'mma repeat something from my previous post:
Yes you can use ir-GTS to check the IVs however, there's a built-in Pokedex IV-Checker in RNG Reporter (I first used the one on Serebii but this one's easier since you can actually right click and copy :P).
Now here's something new. I'm not sure if you have ever worked with IV Checkers before but the one in RNG Reporter is pretty much the same as anyone you've ever used before only that you can't put in EVs since it's pretty much meant to find your parameters. You put in the species, nature, trait, level and stats and it will calculate the range of IVs for you ^^
So there's no need of switching between DS's or the use of another external program. I think a Timer0 is related to a game+DS combination only meaning that switching won't really affect the Timer0. Meaning if you play the game on your 3DS and then go back to your DSO (i'll be using this from now on for the DS Original XD) the Timer0 will still be the samen for that combination.