Just a clarification. The screws (bolts) on the back side of the housing do not adjust the brake pressure. They balance the brake shoe to drum clearance when the brake is released. The nut on top of the brake assembly under the cover adjusts the brake pedal travel. They should be adjusted so that the left and right brakes are evenly applied when you push both pedals with one foot and the brake lock can be applied and hold a heavy application of the brakes. At this time you can then adjust the balance screws on the back side of the housing. Do this by applying the and releasing the brake and watching the movement of the front and rear shoe. Adjust the balance screw (with the brake pedal released) so that both shoes move the same amount.
You should be able to see the brake lining on the shoe to determine how much lining material is left. Make sure they are not worn down to the rivets. This will score the brake drums. Looks to me like a lot of work to replace the drums.
Hope this helps.