As far as funny smells or tastes, you might get a sulphur smell and/or taste initially if you do get it going because of so much SO2 in the must, but it will dissipate over time. There should be no need to add any more k-meta to the must through at least the first racking and maybe the first 2 rackings. I'd go through 2.
The longer a juice must sits without fermenting, the longer the flavors have to change and dissipate into the air, so it is ideal to get it going on time. But since you're in for a penny now, might as well be in for a pound and try to save it.
If it were mine I would grab the stoutest fermenting yeast in my arsenal, like EC-1118 or a champagne or something robust.
I goofed with a measuring error like this once and never could save the apple must. It went to feed the bacteria in my septic tank. It didn't go there, though, until I tried 3 times to save it!
Denise steers you right in how to save it, if it can be saved. Best of luck!
UNDER EDIT: A yeast starter is something you make up, not a supply. Lots of ways to make one. I make mine by boiling a cup of water, taking it off the heat and then adding about a half cup of sugar to it while stirring until dissolved. Then once it cools to 100 degrees F (lukewarm to the touch) I pitch the yeast on that and cover with a paper towel. In just a little while the yeast will wake up.
What Denise is saying is once you see activity in your starter, you should add a little of your must to it. I would add maybe half a cup and let it go for awhile. Check on it, and if the yeast seem to be doing OK, I would add another half cup of must.
Check on it again later and if they are doing OK and working away, then I would think about gently pouring the starter solution on top of the must in the bucket. I would leave it on top and not stir it until the next day. This allows the rocking and rolling yeast to gradually get into eating on the tainted must. If you succeed in acclimating them, your must will become wine.
Like I say, lots of ways to make a starter and I am sure others will chime in with theirs. Good luck!