As someone who sees a lot of different assemblers I really enjoyed this read. But the most important lesson learned for the next CTF: Just probe the PRNG and see if it is predictable :P
Usually out of pride or the sunk cost fallacy (or something like it) I'll convince myself there was no other way the problem was going to be solved. Either way the next time around I spend just a little bit longer trying to think of an easy way out.