"Wait here a little."
Yep, that does not sound right. With limited wait подожди works way, way better. Or you can say "Жди тут!" without specifying for how long. But that's not what it says in this sentence :).
In this course I often use "wait a bit" as a translation for "подождать", which is only one of the possible interpretations. But it does work.
As a part of a larger sentence, "жди здесь немного" might work. In a certain meaning.
подожди or жди :) "Подо" is a variant of "под-" prefix, not a combination of по and до.
"Жди два часа" does work. It is important to understand that imperatives are a bit more complicated than the limited number of such forms given in the course. When you focus on the process, imperfective is your natural choice. When the imperative is used for an action that is limited in time or "point-like", and, in principle, perfective aspect can be used, in practice both aspects are usually possible—depending on context.
The use of the imperfective aspect for "simple commands" is associated with an urgent, immediate action that is understood as "obvious" to the listener. Naturally, it is also used with a few verbs you often say when having guests ("come in", "take of your coats", "sit down" etc.)
One consequence of such interpretation is that imperfective can also be used to demostrate agressive behavior (if the action you imply is obvious in the situation, in fact, is not obvious).