Using H-bridge module and PWM

Hi.

I'm thinking using one of this module to drive a DC motor :
http://www.evola.fr/product_info.php/controleur-moteur-l298-double-pont-p-131

It's a quite standard module we can find on Ebay.

My questions are :

My DC motor can take a little more than 2A (2.5 or 3A) for some 10 seconds under 12V on high torque demand.
On top of that, it's a little bit too fast for my purpose, so I was thinking using the PWM resource of ARDUINO to lower the 12V voltage transformer and slow the motor down.

Will it still take the same current under lower voltage ?

In case not, would I be able to use the 2 channel of the H-Bridge module to get 2 x 2A ?

It seems I need 2 pin to drive the module. It means, for 7 motor, I will need 14 PWM pin from the ARDUINO.
Or could I use 1 pin for the direction of rotation, and 7 PWM pin for the command of each motor. (I don't need different direction of rotation at the same time).

I'm not sure what you're thinking of doing to the 12V supply. Applying PWM to reduce the output of the transformer sounds rather dodgy to me, if that's what you have in mind.

What you can do, though, is use PWM to vary the proportion of time that the motor is switched 'on'. If you only switch it on 1% of the time it will run very slowly (if at all) and if you switch it on 100% it will run flat out. This is without changing the supply voltage.

Since motors are inductive, the current rises slowly and you may find that if you keep the duty cycle and pulse length short enough then this will prevent the current from becoming excessive or at least prevent the controller from overheating.

Since it's a separate board and not a shield, you have a free choice about how you connect it to your Arduino. So yes, there's nothing stopping you from using a single Arduino pin to set the direction of all the motors, and then have a separate pulsed output for each motor to control its speed using PWM. If the Arduino you're using has enough analog output pins you can do this PWM in hardware, otherwise you'd need to use a digital output pin and have your sketch pulse it at the required duty cycle/frequency.