At 35 A continuous drain current, the device dissipates about 21 W in conduction alone at that on-resistance, so the 80 W power dissipation rating at the case provides headroom for switching losses and ambient derating. Gate charge of 33 nC at 4.5 V tells you the gate-drive energy per switching cycle. A 4.5 V logic-level drive is sufficient to achieve the rated Rds(on), which simplifies the gate-drive circuit in low-voltage systems.
The 80 W power dissipation rating assumes the tab is properly heatsunk through the board — without a good thermal via stitch to an inner-layer plane, the junction temperature will exceed the 175°C limit well below 35 A continuous.