How to determine the phase margin and transfer function of this bode plot?
Gain Margin


Find the frequency where the PHASE becomes -180 degrees. 
Find the GAIN, G (in dB), at this SAME FREQUENCY (from the upper plot)
Then, we define the GAIN MARGIN as: Gain Margin = 0 - G dB
Gain Margin = 1/M if you are measuring Magnitude (M) as a ratio (not is dB). 


(Note that G is in dB here... But you may want to convert between dB and magnitude as a ratio. To covert magnitude, M, to gain in decibels (dB), G, you use G=20*log10(M). To convert G to M,  M=10^(G/20)) 


  Am I right, ... that the amplitude margin is 100 dB?


Yes the gain margin is \$100dB\$.



Phase Margin


Find the frequency where the GAIN is 0 dB. (This means the output
and input amplitudes (magnitudes) are identical at this particular
frequency; on the Bode plot, it's where the transfer function
crosses 0 dB on the upper [magnitude] plot.)
Find the PHASE, P (in degrees), at this SAME FREQUENCY (by now
looking at the lower plot).
Then, we define the PHASE MARGIN as: Phase Margin = +P + 180 degrees



  Am I right, that the phase reserve (margin) is approximately zero... ?


Yes. Using the above technique: Phase Margin = -180 + 180 = Approx 0

(Link to above information)