Hi there,
From 12 mos, nutritionally, LOs only need about two milk feeds per day (which could be bf or cows milk, for example. Afraid I don't know about other sorts). So it would be perfectly ok for you to drop a few Bfs from that PoV. Lots of ppl just give milk in the morning and at bedtime from 12 mos.
Re calcium, there are lots of other foods besides dairy that are high in calcium, eg broccoli, beans, sardines, some nuts... LOs don't necessarily need to get their calcium requirements from dairy.
There is a list of foods high in calcium here:
http://www.iofbonehealth.org/calcium-rich-foodsI'd drop the feeds one by one to avoid engorgement, and this would be gentler on your LO too. really, it's up to you which you tackle first (eg the NFs or a daytime one).
Since your LO seems to really enjoy the comfort aspect of the bf, I'd try to make sure you get in lots of other opportunities to cuddle so that perhaps he needs the comfort less. Also, if it's a daytime feed you're trying to drop, if/when he asks for it, you could offer a drink of water and a healthy snack instead, perhaps whilst cuddling on your lap, looking at a book, for example.