Recursion tends to make for many levels, but that is merely incidental. The essence is the coming back to the same place in the definition again (as the name sorta says).
'tawa', as a verb, always means "move" some how; the question is what moves. With the intransitive, it is the subject; with the transitive, it is the object. The subject brings about the motion of the object, but may do that without any motion on its part (by issuing an order, say, or turning on a magnet).
Your subsequent examples are intransitive and thus not much of a problem -- except for the double 'tawa's, which are merely redundant.
Well, the astronaut version uses 'tawa' for the means, where 'kepeken' seems called for 'kepeken palisa pi suli mute' Oh, you aren't talking about a spaceship! I suspect 'kepeken' is still appropriate, but 'nasin' ought to be here somewhere, for "course" and the like ("vector" isn't quite right since they have direction but not length, but close enough).
Your remark about 'tawa' seems to be the one in use, but is still a bad idea, especially when there are a number of actual and potential preps that no one has tried -- 'nasin' for one (with or without 'lon')
'la' phrases are still conditions, but "condition" has a somewhat different sense. All this needs some work through.
Note that 'tawa mun' also means "go to the moon" which could be confusing.
I am leery of 'pi' with verb phrases, but they should be legal -- just not used much, since other tricks are available -- PP and 'la'.