Can arabic gum substitute for fat in making ice cream from homogenized 3% fat (low fat) milk
I don't think I've tried this in ice cream, but a trick I picked up for sorbets (via looking at commercial product ingredient lists - often boring and full of things you can't get at home, but sometimes there's a useful nugget hiding in there) was to add pectin - the "regular" stuff, not the pink "low sugar" stuff (misleading - it's for "low sugar" canning, so it's mostly dextrose, or corn sugar - regular pectin is mostly pectin.) I'll use a tablespoon/15 ml for a 1.5 - 2 pint batch, and 3 Tablespoons/45 ml for a gallon batch (3 quarts liquid before freezing.)

Regular pectin mixes in quite nicely. The low sugar stuff is highly annoying (got a box by accident once - won't make that mistake again.)

I don't know if there's any compatibility issue with dairy (or not), I simply have never even thought to try it other than with sorbets/popsicles that are non-dairy. A quick look shows people using it to stiffen yogurt that isn't making it on it's own, so I think you'd be good there. For that matter, some lowfat/nonfat yogurt might also be a good ingredient for your lowfat ice "cream" attempts.