"did obey" can only be imperfect or present perfect
Really? It can't be pluperfect? How would it be phrased if it were pluperfect?
Actually, I spoke too generally. There are some situations where what looks like a simple past tense in English would be better in Latin as a pluperfect. "He was angry because I slammed
the door in his face" (imperfect in English, pluperfect in Latin) would be a good example, but that can just as easily be rewritten "He was angry because I had slammed
the door in his face" (pluperfect in English and Latin). I think this is just a loosening of English grammar that allows us to say such things without a change of meaning.
i still have problems distinguishing (in English) perfect and imperfect, i.e. whether a verb indicates a complete action.
For example, texts seem to indicate that the phrase "i worked" is imperfect, leaving open the possitility that i am still working.
"I worked" is in English imperfect, whereas "I have worked" is the English perfect. The roles of Latin imperfect and perfect do not match up with those in English, so English imperfect can be either perfect or imperfect in Latin (English perfect can be translated with Latin perfect in any strict translation though).
"I worked" can be perfect or imperfect when translating it into Latin, depending on what you mean by it. It is very difficult to explain the difference between these two tenses through English examples, since even in a context you can often approach a verb from either angle. Continuous and habitual actions belong to the imperfect; simple and completed actions, as well as past actions seen as having an effect on the present (translated in English perfect with "have") are translated with perfect.
"used to ____" and "kept _____ing" are dead giveaways for imperfect, and "have/has ______(ed)" is a reliable indicator of perfect. I think experience with reading Latin will help clear this up, since it can take a context even larger than a single sentence to make the nature of an action clear.
flebile nescio quid queritur lyra, flebile lingua murmurat exanimis, respondent flebile ripae