weeeell... Can you?
As in target wifi only?
You have these options:

Yes Iv seen those but Im referring to the local ISPs, for instance in Greece you have Forthnet, Otenet, Hellas Online etc.
They are the ISPs you actually get your residential block of IP addresses you connect from home with.
Does not seem Facebook allow you to exclude some of those in targeting yet unless there is a less obvious way to go about it...
No, you can't exclude within FB. One "smart" way is too exclude people who liked the ISP you want to exclude. Most likely they have a subscription there.
It's not accurate (also because most are on WIFI after all), but at least you exclude a bunch of non relevant people still....