The most likely answer to your question is that your Eevee simply hasn't got enough happiness yet. That might sound unhelpful, and it might not be what you want to hear, but besides the unlikely possibility of an issue with your game, it's the only explanation. You have done a lot to increase your Eevee's happiness, so I am sure that it is not far off from evolving into an Umbreon. If you continue doing what you are doing, your Eevee will evolve very soon.
Many people ask questions like yours as to why their Pokemon isn't evolving for happiness, so perhaps the requirement is higher than what people anticipate. The specific requirement is 220 happiness points (if that means nothing to you, click here for an article that'll put it into context). Once your Eevee reaches that number, it will be able to evolve.
The game never gives a specific explanation of what your Pokemon's happiness value is, but you can get a good idea of it if you go the happiness "rater" in Laverre City. (There's also one in Santalune City, but they're less helpful.) Their description of your bond with the Pokemon indicates how high your Pokemon's happiness is. You might be able to get an idea of how far off you are if you check with the happiness rater. Use this table to find out what each description means.
I hope this helps explain things a bit!