Yes the path of iron is completely incompatible with getting the getting the Oghma Infinium.
As well it should be, in my opinion. There are far too few choices with consequences in this game. I'm glad some real RPG aspects are added by OOO.
If you take the good Path of Iron path you get some great Paladin Armor (in my avatar at the time of this post, though my avatar may change in the future). There is also the matching sword (claymore) that is fit for a paladin. You also get the satisfaction of helping him out with his grief, versus trying to make him more miserable over the loss of his wife if you take the other path.
So help a good guy out and get a nice set of Paladin Armor and Sword.
Or make him even more miserable for some extra stats.
It all depends I think on whether you want to be caring or selfish. One or the other.