valve must be in wrong way, pushing brakes is pushing air in to the inlet causing increased revs

the valve should allow the engine to suck air from the brake booster, take the valve out (disconnect hoses from both ends) and ensure you can do that (by sucking on the inlet manifold side) to check it is installed in the correct direction, if it has an arrow that should point towards the motor side not the brake side

eidt[] the brake lights is probably the switch as said above, the brake pedal actually presses this switch in to turn off the brake lights, it may need adjusting but more likely the plastic piece that actually pushes it (part of brake pedal) has perished, these are often replaced with a bolt and nut on the ol' dattos these days