Driving 74HC logic with sub-nano second clock reference
It's all about capacitances.

74HC-whatever is too slow for that. Input capacitance for each "block" of your circuit is 3.5pF. This is flattening your 0.4ns pulse.

ST9011 transistor is too slow too. Datasheet says: 370MHz bandwidth and 1.5pF collector-base capacitance. You probably also have some extra parasitic capacitances there.

400ps is quite short time, maybe not enough to charge your whole circuit capacitances. Wiring and PCB are very important when you deal with such short pulses or high frequencies.

You need ~2.5GHz transistor and correct wiring/PCB to eliminate parasitic capacitances.

2.5GHz because 1/0.0000000004s = 2500000000 Hz

High frequency transistors are not expensive, I just found random 6GHz transistor (BFR93A) and it costs less than 0.30$ where I live. You may look for something with higher gain or just try this.