In a close quarters battle reaching for your gun may not be the best choice. Remember, the root word of gunfight is fight, not gun. From contact distance to about 3 feet, you can strike your adversary, hard, and use those blows to create distance and decide if you need to reach for your gun. Using a kubaton, marker, flashlight or other impact weapon to increase the power of your strike will provide maximum benefit to your aggressive actions.
There is no reason to allow strangers to approach you. We live in dangerous times and we see now that we must be ready for anything. If someone you don't know approaches you, challenge him or her. Be prepared to defend yourself to the best of your ability. Use every level of force that is warranted, from a verbal challenge, to alternate weapons, up to and including deadly force if you must. Refuse to be a victim. Prepare yourself.
Choosing to carry spare ammo for your fighting pistol is a good idea. Just remember to select the right spot. The most common place for a concealed carrier to hang a spare magazine is on the off-side hip. This makes for a very direct and fast reload and does not force you to reach across your body.
Training yourself to carry, access and shoot your weapon with your "other strong hand" is something that will certainly take time and repetition. Just like your other training, start slow for form and pick up speed as you improve.