I don't have Crohns or liver problems, but definitly have the low iron. I have something funky going on GI-wise, but no dx as of yet. My ferritin was 7 when first tested. Dr put me on 75mg of ferrous succinate daily.
Its possible that the Crohns is interfering with your iron absorbtion. Most Gastros will suggest getting an endoscopy and colonoscopy done to rule out any GI bleeding as being a contributing factor to the iron issue. I just had this done 3 weeks ago and everything came back fine.
The anemia board has lots of good info regarding both low iron and GI exams, so you might want to check over there.
Please keep us posted.