Nice work, pito! I take it you live on Easter Island.
Having visited there for a couple of weeks some 20 years ago, I imagine that you feel a bit isolated (in terms of technical interests).
Regarding the topic, I'm wondering if the preamp can be dispensed with and a fast comparator with positive feedback (to introduce hysteresis) coupled directly with the photodiode could be used. I will try some design simulations along those lines. Incidentally, the BPW34 PIN diode has 25 pF capacitance at 3V reverse bias, so your simulations were spot on.