In your situation, first I'd spend money on the things that may well PREVENT you from ever having to use the gun.
1. Install extra locks on the front door, locks that can be armed from the inside and install an anti-splinter gaurd on the door. Contrary to what you see in the movies, it is very, very diffcult to kick in a door, espeically one with a high fire rating like code requires for apartments. It's more likely that the bad guy will shatter his leg than it is that he will get in.
2. Install an instant-on alarm on the front door that is armed when you are inside.
3. By your bed, get a corded old-school phone with a speaker phone and have 911 on speed dial. Once a bad guy knows 911 has been called and the cops are on the way, he is far more likely to retreat without a shot being fired.
4. Get two high-quality tactical flashlights. One by the bed, and one stored safely in another location that is easy to get to in case the primary light fails. For obvious reasons.
If it does come to a shootout, it's most likely because of a failure to secure the building and that's the fault of the owner. A middle of the night shootout with a crazed nut-job is a VERY bad situation. The smart money is spent on avoiding it. You already have what you need to deal with it should it happen, but the smart thing is to prevent it from happening by whatever means are available to you.
Grouse