I had the same problem back in 2000 it was horrible going to the bathroom was hell i cant remember the name of the medication the doctor gave me i believe it might have been nitro(something) they use it in the hospitals and it is very powerful u can only use very little at a time.... I saw a general surgeon after two months of pain and i had surgery what they do is cut the sphincter mussle to allow passage... And 150% it totally worked... See a general surgeon...
As a former anesthesiologist, I am more into cutting things out than putting creams on them... generally speaking, that is. An anal fissure is a tough thing to heal-- the frequent stretching pulls apart any healing process every day or two, regardless of the softness of the stool. Along that line, though, water is one thing, but if that is the treatment plan I think that you should be adding a softener as well, such as the ones made by dulcolax or others. One bout of constipation is going to destroy a couple weeks worth of healing!
The itching comes from the constant exposure of lymphatic tissue to millions of bacteria and yeast, resulting in the release of inflammatory mediators including histamine. While not made especially for this purpose I would consider using an antihistamine-containing cream; something that contains diphenhydramine for example. You may also want to try a dab of 'bactroban' ointment to keep infection from gaining hold.
Finally, you may want to search the forums for an opinion from a general surgeon. While surgeries always carry some risk, an anal fissurectomy is relatively minor.
JJ