2000 Jeep Grand Cherokee Laredo----I need Help Please----

My 2000 jeep Grand Cherokee Laredo dies randomly and I can't figure out what needs to be fixed. The jeep dies sometimes going down the freeway doing 60mph, sometimes when coming up to red light or stop sign, and sometimes it just won't start )it has this problem in rain, sunshine, hot or cold, weather I have a full tank of gas or at a quarter tank) There are no warning signs and I don't loose complete power. The engine just shuts off and drops down to 0 rpm but the radio and lights still have power. There is no sputtering or stall before it dies, it just dies and the brakes and power steering are lost. Sometimes it just starts right up after dying and then other times it can take hours or days for it to start again. It has never had a check engine light come on (still after 5 months of this problem) I drive 20 miles to work and on average it dies 3 or more times each way on a daily basis. I have had the crank sensor replaced(it wouldn't start for a week then we replaced the crank sensor and it started right up and drove fine for about 4 days then again started dying daily), the idol control valve replaced, the battery replaced, the alternator replaced, and have checked the fuel pump relay. Recently, one of the mechanics told me they are pretty sure its the fuel pump or a clogged fuel filter, but I was just wondering if anyone can offer some insight before I spend even more money on parts. Also, recently the ignition has been having problems. One day I was trying to leave work and after trying to start my jeep for almost an hour, I took a break and went back inside when I came back out to try some more, the key wouldn't turn. A locksmith told me to take WD 40 and grease my key then tap with a screwdriver. This worked but since then it has still happened several times, the reason I am mentioning this is because he said something about my theft system killing my car. Several times now it has died while driving and then when I try to restart it the ignition is locked and the key won't turn, so I am not sure if maybe he was right and the chip in the key is shutting off my engine. (I thought he was crazy when he originally told me this might be my problem because the dying problem has been consistent for about 5 months or more and the ignition is a recent problem from 2 weeks ago) Any thoughts or helping tips would be greatly appreciated. I have a four year old that I refuse to drive in my car because I live in a big city with lots of crazy traffic and too many times now it just dies in the middle lane and I am stuck like a sitting duck with my hazardous on hoping people don't hit me. Please help