Experiments to convert analog 10ns pulse to digital 10ns pulse
1 - 10 nA to 100 mA is 70 dB, not 60.

2 - I am astounded that you're getting acceptable results over this dynamic range. Running a TIA to give 50 mV for 10 nA will produce 500 kV for 100 mA, and frankly I'm having problems believing that you have designed and built a TIA with that sort of clipping/overload performance. You also have an effective transimpedance of 5 Mohm. Granted that you're using a much lower transimpedance followed by voltage amplification, getting adequate speed in this setup is not something I'd want to try, and the dynamic range of the output chain remains at wildly improbable levels. Assuming, just as a SWAG, 1 nsec rise and fall times, a perfectly compensated TIA with a single pole response will need 350 MHz bandwidth, rather than 100 MHz, and the subsequent amplifiers will also need that bandwidth or better. I suggest that you take a long hard look at your test setup, from your test emitter all the way down, and make sure you're not fooling yourself about your results.

3 - I also don't think I believe your results on the basis of noise. Assume, just for instance, a 10k feedback resistor on your TIA. This will boost a 10 nA pulse to 100 uV. At the same time, Johnson noise from the feedback resistor combined with a 350 MHz bandwidth will give you 240 uV rms noise, which is not what I call a good SNR for measuring pulse width. Note that going to a 1k resistor gives 10 uV signal and 75 uV rms noise, so you want your transimpedance as high as possible. This, of course, will bang head-on with your amplifier speed and stability.

Like I say, I'm very skeptical about your claimed performance. Unless you post a detailed circuit showing how you got it, I think you're kidding yourself.