Well, to begin with, you've got three actual NHLers (one of whom is a UFA) for two (both of whom are UFAs) and two prospects, so right there you have an imbalance. (Let's put aside for the moment the issue of whether the draft picks make up for that.) Moreover, UFAs are essentially worthless to teams like Chicago that won't be playing in May. In contrast, the UFA the Maple Leafs are getting is HIGHLY likely to be valuable to Toronto during the playoffs, especially inasmuch as he's having a better year than Kerfoot on a much, much worse team, so he can be expected to contribute even more than Kerfoot has. So that's a clearcut loss for Chicago that the third and the future second only partially redress.
Then you've got a fourth-line NHLer vs. the value of two prospects, neither of whom are all that exciting. So if we ended the analysis (and the trade proposal) there, Chicago would probably be worse off.
The BIG problem with this idea is that you've massively understated the trade value of a guy who's going to be your #2 LhD for THREE playoff campaigns, at an almost ridiculously low cap hit. McCabe's value by himself is probably a first-round draft pick, if not more -- look at the offers being bandied about on CapFriendly (and some among the pundits) for Vlad Gavrikov, who is a UFA. But let's say that I'm overestimating McCabe's worth. Then at the very least we have:
McCabe = future 2nd plus one of the prospects (and I'm being generous)
Domi >> Kerfoot, Holl and the third
Lafferty > the other prospect
In short, Chicago is getting robbed.