Yes dot4 for the brakes, that's what will be in there now.
Have you checked your brake pads recently? They are probably worn and some might need replacing
Very rare to need topping up. Follow the rear brake lines down, especially where they cross over the rear axle. Check for any dampness. If you have stainless steel braided flexis then check the ends for weeping.
Here at LandyZone we have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.