Excellent question! The answer used to depend on the type of book being transcribed. With the release of the new Formats Guidelines, the answer to this question is very simple. EBAE is now the governing code book for this situation. There is no longer any need to differentiate between literary and textbook, they are both treated the same. Yes "to, into, by" should be contracted and joined to letters. See EBAE Rule XIII Sect. 41 and Rule II Sect. 12.a.(2).