Welcome! It's great that you've got a Big Brave. This is one of the better-playing Gottlieb multi-player EMs. I have this game, and I really like it.
Here are some answers to your questions.
You should be getting 5000 points when you knock down the last drop target. 10K points or more is definitely not right. If I had to guess, I would say your drop targets may not be resetting properly. All the drop targets should solidly and firmly pop back up on the first 5000 points scored after getting them all down. If they aren't, check the reset bar on the drop target bank to see if it is binding mechanically. The plunger and sleeve on these bank reset assemblies are often very gummed up and so they stick. Cleaning the plunger and the inside of the sleeve (or better yet, replacing the sleeve) often helps.
For star rollovers that don't score, it's probably due to dirty and/or mis-adjusted switch contacts on the sequence bank (relay bank) mounted on the underside of the PF. There is one relay for each letter B, I, and G. There are make-break switches on each of these relays that connect the corresponding rollover switch to one circuit when the relay is latched, and a different circuit when the relay is tripped. In this way, a star rollover can score one thing when not lit, and something else when lit. So if the rollover is dead when its corresponding relay is latched, the make-break switch points are probably not making good contact.
Also note that the sequence bank frame fits into two end brackets and there are wing nuts that hold the frame in the brackets. On Gottlieb EMs, if the frame is loose and has slipped out of the end brackets even a little bit, then the relays will not operate correctly. So you always want to make sure the relay frame is properly seated in the end brackets, and the wing nuts are cinched down very tight.
If your replay unit isn't adding credits, it most likely is that the pawl on the drive arm that pushes the gear is stuck on its pivot. If the pawl is stuck, you can put some penetrating oil on the pivot of the pawl on the drive arm and work the pawl back and forth by hand to free it up. Then you should start getting added credits again.
For the playfield lights, in addition to the fuse holder, check for a dirty switch on the tilt hold relay. This switch needs to be making good contact when the tilt hold relay is energized, or the PF lights will go out. This switch is what causes the PF to go dark when you tilt the machine during game play - the tilt hold relay drops open, shutting off both the lights and the power to the PF coils until the ball drains.
Have fun and again, welcome! - TimMe