Sounds like you have a lot of problems on your plate, I would start with not driving it daily. I had a similar problem with my s14 , it would cut off while I was driving.
Plug what ever was connected to that gold box back. Then check the alternator to see if it went bad. (pull both battery cables from the battery after you get it to start) If the car shuts off after you do that, then you have a bad alternator. Replace it.
Also be aware that you alternator still may be bad if it passes that test. The diode (I think that's what its called) if damaged or worn may still continue to draw energy from your battery even after the car is turned off. Which may cause you car to not start after you shut it off, or all the electronics in your car may shut off and not turn back on for a while.
After all that hopefully your car will start, if not then I would check the battery to make sure its not bad. You can take it to a pepboys or some thing to check it they usually do it for free. After you know you have a good battery clean all the terminals with sandpaper until they look clean. Make sure your battery's ground cable is securely grounded to the motor and to the chasis( that's how its connected in my s14 from factory) and free of corrosion. Connect everything back to where it was, and it should be fixed.
If its still not fixed check the starter then the ignition switch it may have gone bad. This is what happened in my case. As for the sputtering start with a full tune up, and go from there. I do not know if what I told you is the best way to go about it, its what I did in order to fix my starting problems, and it worked for me. Maybe some of the other members may chime in with more advise if your having more problems after all that.
Cheated on the sentra with a 240
, I wouldn't have it any other way.
Fully built DET is on the way.