If you check figure 3 you have Id = 30 A @ Vgs = 5V, that is what tripping me off a bit. If you needed saturation current (or similar) then a minimum power should be stated.
Or am i totally missing the point?
Yes, that graph is for Vds = 25V, so if the voltage is 25V the current is 30A, an on
resistance of about 1 ohm, not 0.008 ohm if you drive the gate at 10V.
The graph in fig 6 is the killer - the gate plateau doesn't even start till 5.4V or so,
the plateau is the point at which proper conduction starts to happen. You normally
want drive voltage about twice the plateau voltage.
The only spec you need to look at is the Rds(on) spec - for this device its quoted
only for 10V, which means you drive the gate at 10V or higher, end of story.
Note that all the graphs are "typical device", and there is significant device
variability not reflected in them (gate threshold / plateau voltage has lots
of variation, about +/- 1V, note).
Anyway if you are building a high power H-bridge you need to use proper hi-side/lo-side
MOSFET drivers capable of pushing a few amps into the gates. Most automatically
generate a bootstrapped hi-side gate supply rail using an external diode and capacitor,
using the PWM signal to pump charge. Look at the datasheets for chips like the
HIP4081, FAN7388, FAN7392, IRS2001, etc etc etc
PS these days there are better MOSFETs available than the IRF3205, such as the
IPB017N06N3 (1.3 milli ohm)