Does a TN deity allow all alignments or just ones one step away? Such as Ogmha supports LG and CE? Or is it a little more nuanced?
The 'one step rule' is not a universal law, merely a 'rule of thumb'; a guideline. Many deities allow different alignment combinations; a common combination is LN, NE, and CN. Clerics of Gond can be of any alignment. I would expect, however, that any cleric of any deity over time, as he or she gains levels, power, and favor with the deity, would grow ever closer to the deity's goals and hence alignment.
Some deities have listed only a single support domain. I take it these are not permitted deities for clerics?
Typically, such instances are simply oversights due to the difference between tabletop and Neverwinter Nights domains. In the case of Hathor, healing has already been added to her list of permitted domains as discussed here. I have alerted Tellenger to the issue with Horus-Re, and recommended the addition of War to his domain list. When it is modified, I will inform bighairyandy so that he can amend the contents of his post to reflect the modification.

If any further examples are noticed, please add them to this thread.

Do not meddle in the affairs of dragons, because you are crunchy and taste good with ketchup.