Locking screen doesn't prevent pigs from getting FDE encryption keys. Running Tor exit is great. But I suggest not doing it unless A. You are a University B. You are the EFF or have good lawyers on your team C. You are some other organization failing the above three D. You have absolutely nothing illegal on your PC, and do not have anything illegal in your home E. You run it off of a server in a data center that can not be traced back to you too many people have been raided due to what their exit node was seen doing, it just is not worth it to run an exit if you do illegal shit that will be discovered during a raid.