Why aren't my Enchanting and Alchemy fortifying each other correctly?
Solution 1:
SOLUTION!!!
I can confirm that I too had this issue on the PS3. No matter what I did I could not get above 22% in my items with same information you have given.
I went into game data on the ps3 menu and deleted the game data and the game update for Skyrim. Launched the game and let it patch and reinstall the game. I then went straight to an enchanting table and with no enchanting gear I could create +25% alchemy gear using Grand Gems alone.... I edited a section on Wiki about bugs and stated that I confirmed a solution to this problem.