Inductive kick-back voltage calculation
Your calculations are right.  

However, that assumes a perfect inductor. A real inductor has interwinding capacitance and parasitic capacitance will will cause the peak voltage to be a lot lower (try it in SPICE with/without e.g a 100pF capacitor in parallel with the inductor)
Also things like air ionising will stop the voltage reaching huge levels under normal circumstances.  

Basically, the voltage will rise towards the peak until (usually) something gives, which is hopefully not your transistor/IC or whatever else you want to remain operational.
So something in parallel to allow the voltage to find an easy route of discharge is necessary, like a diode or a resistor/capacitor.
Any diode capable of turning on quickly enough and handling the brief 1A current would do, the BA157 should be okay (I'd say the 1N4148 is borderline with that current)  

Note the the discharge time will be proportional to the voltage across the inductor, so if you need faster discharge then you can either put a resistor in series with the diode, or just use a resistor in parallel instead an calculate for the maximum allowed voltage rise. Another good option for fast discharge is a zener to clamp to the maximum allowed voltage.
Since all these methods raise the voltage drop across the inductor, it will discharge faster.