Edit: mostly ninja'd
If your health is at 85% or higher, you will regenerate slowly. Also the doctor at SGS (and in a few other locations later on, potentially) will heal you for free.
There is a narrow little button at the bottom middle of the screen, click it and drag things down to your hotkey slots. Or drag things from your inventory there (like lockpicks, haxxors, crowbar, healing items, whatever). You disarm a trap, just put the cursor on the trap and click. Stealth is a hotkey button, so is pickpocket. You need to rightclick your lockpick/haxxor/whatever to use it on something, or hotkey it. That's all the skills I can think of that you'd use on your environment besides combat stuff.
Lockpicks and batteries are not expensive. Little tip: do a specific thing for Old Jonas and he gives you a discount, and he sells both of those things.