The DR number, Diederich Rank, refers to the highest number in Diederich's frequency listing, which you can see here: Diederich Ranking.
DR 46. Non multa sed multum. You can also find this saying in the form: Multum, non multa. The contrast is between "many things" and "much" (i.e. deeply, fully, etc.). Instead of trying to accomplish many tasks, you should do fewer tasks but with much care and attention.
DR 46. Quid multa? Here the word question word quid has the meaning "why?" or "for what reason?" Compare the English saying, "Need I say more?"
DR 47. Ex uno multa. This is one of the sayings Erasmus included in his Adagia, 2.1.49. The idea refers to any circumstance in which someone is able to take one thing and turn it into many things, to such a degree that the result may seem paradoxical.
DR 51. ad hominem Also found in the form "argumentum ad hominem," this is a logical fallacy that bases the attack on the personal qualities of the opponent, not on the topic in question. You can read more about this fallacy at Wikipedia.
DR 52. Habent omnia tempora sua. Note the distinction between the subject, "omnia," and noun phrase "tempora sua" which is the object of the verb.
DR 52. Omnia tempus habent. These are the opening words of the Biblical book of Ecclesiastes 3 and it is included by Polydorus in his Adagia, B338.
DR 52. Omnia tempus habent, omnia tempus habet. Note the different verbs: for habent, omnia must be the subject, but for habet, tempus must be the subject!
DR 53. Etiam si omnes, ego non. Notice that the verb is unstated here, and can be supplied from context. This is the motto of Clermont-Tonnerre.
DR 57. Non possunt primi esse omnes omni in tempore. This line of verse is cited in Macrobius's Saturnalia, 2. Notice the elegant way "omni...tempore" wraps around its preposition!
DR 57. Primus sum egomet mihi. You can find these words in Terence's Andria. The word "egomet" is an emphatic form of the pronoun "ego."