Congrats, looks like a nice car. looks like you have the fuse box covered.
Horn - Foam under the ring can be replaced by a piece of old mouse mat. Wire from horn comes up inside the steering column so you'll need to check the continuity. Horn ring shorts this wire to earth. Often gets broken some where and it has to jump the flexi joint. Replace this if it looks to be delaminating.
Stiff point at straight ahead position often caused by someone tightening the screw in the top of the steering box a bit too much. Try loosening the lock nut and backing out the screw a quarter turn and then locking it back up. Better to jack up the car with a shop jack under the front cross member until the wheels are just off the ground. Then check the stiff spot and adjust accordingly. With jack stands under the 2 A arms you can also check for stiff joints.
Hot brakes - Check that the wheels spin easily with them off the ground. Pucks in front calipers stick easily if car is left standing. 3 pucks each caliper. You might get away with easing the pads back with a lever. That will give you an idea if any of them are sticking. Rears seize up if parked for a long time with the handbrake on. Handbrake cable can also seize up. Beg or buy the proper puller for the rear drums before you attempt any work on them. Pukka Volvo one the best but there are heavy duty 3 leg pullers that work too. They must pull from the centre and not on the outer edges of the drum.
Lots more but you can only do one job at a time.
Work safely!