Sounds/looks good, except you use the drop from 5V to 3.3V (nominal Vclamp) to calculate the pullup resistor for approx 2mA quiescent current shared between the TL431 and its voltage set divider. 2.5K starves the TL431. Try 1K, as the divider only takes 1/4 mA , that gives about 1 1/2 mA for the TL431.
N.B. the cap wired A-K across the TL431/TLV431 ie *IMPORTANT* for the clamping transient response as the high frequency gain of both shunt regulators sucks.