Thursday 13: Hawaiian Alphabet

An interesting fact... The Hawaiian alphabet has 13 letters. What's that, you ask... what are those letters? (Okay, so I know none of you truly care that much, but play along anyway.) And therefore, in no particular order, I give you each letter. Well, not really. Just a hint at determining each letter. I'm not just going to cop out and list letters after all. That would be boring...

1. The only Democratic president that had first and last names beginning with the same letter. Name the letter.
2. The symbol of the chemical element with atomic number = 7. The chemical element is used to preserve the freshness of packaged foods, to reduce fire hazards in military aircraft fuel systems, and to pressurize kegs of some beers.
3. A 'y' is a Greek one.
4. The vitamin associated with retinas.
5. Bernard Lee, Robert Brown, and Judi Dench all have this letter in common. And I'm not talking about the respective letters in their names. In fact, this letter doesn't appear in any of their respective names.
6. A common modern abbreviation for a second-person personal pronoun.
7. The more senior agent, he read tabloids and spoke to Remoolian pugs.
8. One of two Republican presidents that had first and last names beginning with the same letter. Name the letter. (And it isn't the 'Silent' one.)
9. This magazine almost always has the same person on its cover. And all her life, she's had to fight.
10. The Super Bowl in 2017
11. A very irrational 2.71828182845904523536... according to Euler
12. While watching Wheel of Fortune one day, my grandmother exclaimed to one of the contestants, 'You shoulda took a _'. As small children, my brother and I thought it rather amusing.
13. Not to disappoint, but there is no clue for this last 'letter'. It is a glottal stop best represented by the dash in 'uh-oh!'. Or by the apostrophe in Hawai'i. Go figure...