Disclaimer. I don't know Chinese of any time period or dialect, so everything I say about the language situation is at least third hand -- and possibly misremembered at that.
1 DDJ is around 2400 years old. In that time, even the Chinese language has changed considerably and just what those changes were -- what things meant originally -- is something that can only be approximated (or guessed at with varying degrees of uncertainty) based on what we have of continuous records over those 2400 years.
2 DDJ is a remarkably popular book (said to be the second most translated book in the world) and one about which much has been written. As a result, a lot of interpretation, beyond just trying to reconstruct the language, has accrued to it. It has, in particular, appealed to people of very different philosophical bents, who have read into it much of their various views. And this variety has affected later commentaries, even by those of different persuasions.
3. The China of 2400 years ago was mainly an oral culture. The idea of writing something down for all to see, other than official documents and religious rites (and the odd poem -- I'm not sure where that comes from) is only just about to start, mainly with the followers of Master Teacher Kung and their rivals (cf. the situation around Socrates). So, outside these, a philosopher (for want of a better word) would not write a treatise. Rather, he would or chat about his thought with a changing group of listeners.
4. So DDJ is a mnemonic device, a set of notes that were easy to remember (they were much better at this back then) to remind the sage of the main points and the order of presentation. He would fill in the details as he talked through his outline. For Li Erh, we don't have anything that claims to be a fuller set of note (unlike Kung, where we don't really have the outline). So, anything beyond the text is back to point 3, a compilation of guesses, flavored by all the positions of all the guessers.
5. So, stick to the text as best you can: (in Mandarin pinyin) "dao ke dao fei chang dao", roughly "way can way not everywhere way"
6. Like tp, Chinese (of this period) words had a casual relationship to normative parts of speech but, unlike tp, it has passives -- it just doesn't mark them separately. Words also often had fairly broad meanings: "dao" is a way of doing things as much as it is a physical road and, of course, travelling on and being travelled on. "chang" means "ordinary, common (in both senses)" as well as "everywhere" and "always" (maybe "ubiquitous" sums up a lot of it).
7. Like tp, Chinese is basically SVO, but allows many variations (more or less well marked). It is AN rather than NA, but relative clauses (which it has, more or less well marked) follow the noun. Unlike tp. it does not have obligatory (or even common) markers for Subject, Predicate, Direct Object, or modifier grouping, which opens possiblities not available in tp.
8. The standard analysis of 1.1 is that the first "dao" is the subject, that "ke tao" is a relative clause with the modal "ke" taking the passive verb "dao" as complement. The predicate then begins with a negation "fei", presumably denying an identity of the subject to the predicate noun "chang dao" . Hence the usual basic translation "The way that can be travelled is not the universal way" ('jan li ken nasin e nasin ni la ona li nasin awen ala') . But. even within this grammatical analysis, it might be "not the ordinary way" and, inceed, "fei chang" is -- and has been for centuries -- an expression meaning "unusual", even "special" as well as "weird" ('jan li ken nasin e nasin ni la ona li nasin nasa') . And, of course, other grammatical analyses are possble (more or less plausible) down to, say, "A path can traverse a strange route" ('nasin li ken nasin e nasin nasa')
9. It is general conceded, even by the most hard-nosed, that DDJ is basically a work in the apophatic tradition. It is one of the first with the maxim, 'jan toki li sona la, jan sona li toki ala'. So, why would a putatively wise man write (or memorize) a work ofseveral thousand (ultimately misleading) words? Aside from a true-believer urge to get "everybody" on board, there is the standard technique for this school everywhere: using words to bring one to such a muddled state that one has to pass beyond words to grasp something solid. And it is the Li's successors -- through many changes, to be sure -- that did this best in the Zen koans. Which is not to dismiss more discursive methods ("He who fully understand my propositions will realize that it is all meaningless. One has to be silent about what one can't talk about"). So probably, if you translation hits the sweet spot between apparent clarity and underlying absurdity, you have it right enough for the purpose.