in a resistive circuit.
No - E = I/R
No. The current depends on the resistance, as well as the voltage.
I suspect that your 4.8 V batteries have a _capacity_ of 720 mA-hours or 1200 mA-hours. That is, they could theoretically deliver 720 mA (or 1200 mA) for an hour before becoming fully discharged.
Yes - but it won't run it for long.