The inner seal, the one in the trumpet housing is the one that keeps the brakes dry. the one in the bearing retainer only keeps the grease in the bearing and dirt out of the bearing. Replacing the inner seal may or may not stop the leak. Why not? If the axle play is excessive the bearing allows the axle to lift away from the seal.
How do I check and or fix it? Block the tractor up, remove both rear wheels. Turn one axle flange, the other should turn the opposite direction. Try to push the axle in and pull the axle out. There should be no play. To adjust. Remove a shim or two from between the trumpet housing and the bearing retainer. Reinstall axle, check as above. If both axles turn the same way you need to reinstall one shim until the turn opposite. It is not usually necessary to replace the outer seals, They are a lot of work to replace!!!
The axle bearings are tapered roller, when axles, bearings and other parts wear end play allows the axle to "come out" of the bearing and the trumpet housing "falls down" on the axle this allows the axle to lift off of the bottom of the seal resulting in an oil leak and poor brakes
As for the screws--be glad they are gone-- it they get tight from rust -- well just say it a job to get them out.