Looking at that chart... I feel like there would be many OTK decks based off of it, and also arena decks based off of it so that they can have a better chance of getting more of them at once.
I feel that haveing the possibility of such a buff is a bit too outrageous to become a real card.
Now using your very well made chart in the OP if you don't mind.
I think arena decks would have the same restriction about this than they have with SoSac: can't play more than 6 in a duel. Else they could potentially perform 12-chains (with the help of hourglasses for example), which are things not even foreseen by my formulas and which wouldn't be balanced.
As for OTK decks, this card was pretty much made for such things, like many other cards of my
Chain series. Their disadvantage being high cost and low effect as long as you don't chain at least 3 of them.
Perhaps the first card could go to your strongest creature, and then it affects your second strongest creature and so forth to make it more balanced.
I actually hesitated quite a while about whether the buff should go to your strongest or weakest creature, knowing that the latter would automatically distribute the bonuses among your creatures, but for some forgotten reason i stuck with this one.