The DR number, Diederich Rank, refers to the highest number in Diederich's frequency listing, which you can see here: Diederich Ranking.
DR 25. Esto quod esse videris. ~ Note: This is a motto of the Coke family. The saying plays on the difference between being (esto) and seeming to be (esse videris). As often, the antecedent of the relative has been omitted: Esto (hoc), "Be that," quod esse videris, "which you seem to be."
DR 27. Habeo, non habeor. ~ Note: This saying plays on the contrast between the active and passive forms of habeo; in the passive, "habeor" means "I am held (to be)," "I am considered," etc. The contrast is like that between esse and videri in the previous saying. You can find the phrase used by Cicero in one of his letters, and it is also a motto of the Booth family.
DR 28. Omnia mea mecum sunt. ~ Note: The idea expressed here is that of spiritual self-reliance, where the things that are really yours are the things that are part of your inner character, the qualities that go with you wherever you go. For a discussion of this saying and its related forms, see this blog post at Laudator Temporis Acti. Note also the special form mecum = cum me.
DR 31. Non sibi, sed omnibus. ~ Note: This is the motto of the Ackworth School in West Yorkshire, England.
DR 31. Non sibi, sed suis. ~ Note: This is the motto of Tulane University.
DR 31. per se ~ Note: This is a Latin phrase used in English to mean "in and of itself," intrinsically. It also happens to be the name of some journaling software for the Macintosh developed by a former student of mine: Per Se.
DR 32. Dii omnia possunt. ~ Note: This is one of the sayings in Erasmus's Adagia, 4.6.11. Note the distinctive plural form of the noun deus: dii.
DR 35. in re = re: ~ Note: Yes, this is the "re:" that you see used in the subject line of memos and emails.
DR 35. Res tuas tibi habe. ~ Note: This is a phrase in Roman legal language that a spouse could use to request a divorce.
DR 37. Cui des, videto. ~ Note: This imperative videto, "see," has the cautionary sense of "watch out for" or "keep an eye on." Note again the use of the future imperative, a common feature of proverbial style. This is one of the sayings included in the monostichs attributed to the so-called "Cato."