For me theory is just one tool in the toolbox. But it's not mandatory all the time to utilize that tool to make music. For me, all but your last question could be accomplished (and most of it I have experience doing) without thinking about theory at all in the terms you've stated. For example, on a guitar transposition is easiest of all instruments. Playing 4 hours with variety can be accomplished with experience instead of rote theory, by building up a 'library' of various phrases and things to play over time - doesn't have to come from theory, could just be either copying bits from various music you've heard, an instructional video, or self trial and error. Don't have to understand the theory if your ear is good enough to tell right from wrong musically. Going on the road with 12 hours notice is more an issue of how quick of a learner you are.
Something that seems to remain a tacit undercurrent and not sufficiently discussed is that making music involves a combination of skill and talent, in some varying degree of both. If you can use theory to jump in right away and be productive, that is a learned skill and more power to you. There are also guys who can't tell you the names of the chords they play, but they can sit in with a jazz combo and perform rings around some of the best-schooled theory players, and do it all with much superior feel and soul that really reaches into the heart of an audience, resonates with them, sinking deep into the audience memory with their performance. But theory and talent are still just tools in the toolbox. Some have more skill at their disposal. Some have more talent or innate ability. The key is having just enough of each in whatever degree necessary to make music that would communicate well with others who aren't musicians, even if only for personal satisfaction. Otherwise, why bother at all?