How many letters does the longest word on this page contain?The largest word you can construct from this combination is 'quattuordecillionth', and it consists of 19 characters.
Which word that has 'a' in and ends with 'th' is the most unusual?By far the most unusual word in this list is 'math'. According to the Oxford dictionary, 'math' is defined as "A mowing, or that which is gathered by mowing; -- chiefly used in composition; as, an aftermath. [Obs.] The first mowing thereof, for the king's use, is wont to be sooner than the common math. Bp. Hall.".
How many actual words are possible to put together using the specified combination?It is possible to make 490 words using the specified combination.
Is there a word on this page that sticks out as the most common?The most common word is 'death', which in fact is the 393rd most common word in this list.
What is the highest number of points you could get in Scrabble from this list of words that have 'a' in and end with 'th'?With the number of words to pick from, your best choice is to go for 'hawkmoth' scoring 23 points overall.