The match up really comes down to mind games, grabs, and by extension, Falco's ability to either jump out of grab or break away.
First, ban FD. For IC and Diddy Kong, just don't play it.
Second, head shot. Make it happen.
Third, Chase nana. Separate and chase Nana. You can pretty much space well, charge F-Smash, and she will run into it.
On separation:
Eh...tough... I personally prefer Delfino for this match up because the platforms are wonderful and when on a normal ground, I tend to fight left or right. This way, the main platform will start flying away and a solo popo can't get back if you hit him with some knock back OR Nana might be lost when trying to recover with up B. I can guarantee that unless you are simply terrible with Falco's recovery, you can make it unless the blast zone catches you on the ground.
For neutrals, Battlefield clearly.
For the ratio:
Well, pretty much a mediocre falco versus a mediocre IC is really just ****. I would definitely say that if this were done on the basis of averages it would be near 70:30, however, when both the IC and Falco play as they should, I can see the match as being 55:45 IC favor. Really, the only reason a player should be getting ***** in this match up is because of their lack of knowledge in fighting it or because they always counter pick IC and don't play it enough. It essentially comes down to practice, practice, practice, just like anything else.
And until we have more good Falco's (other than the mindblowing abilities of DEHF) trying the match up and not being successful, I will use the existing example and agree it could be 55:45.