Interesting. Thanks for the detailed remark. Space and time are very useful notions and indeed, it is difficult to imagine a universe based solely on matter and action...and yet mathematically, it is easy to imagine.
You speak of "what is beyond" the universe, but that question presupposes the notions of space and time. You note that:
"Discrete events arise from the interaction between energy and matter. They are enabled by the prior existence of time and space that function as context. Only increments of time 'emerge' between events, which fact helps us distinguish each event from all others."
First of all, you use words that presuppose space and time. An event is necessarily defined by time and has no meaning otherwise. Once you accept the notion of an event, you accept the basis of space and time. If instead you say that matter and action define change, time and space emerge from that action of matter, not the other way around.
Since the math seems to work just fine, the simple approach of matter and action does seem to describe a simple fundamental duality.