HELP! Misfiring, can't figure it out

I have a 2wd 1996 sr5 with 215k miles. one owner and i bought it about 3/4 months ago and have since put on 3k miles.

About a week ago I ran into the store as i was running errands. When i came back out it was idling very rough and my throttle response plummeted. I turned the car off and turned back on and it was gone. Fast forward 2 days and same thing, got back in the car after it was already hot and another rough idle. Except it wouldn't go away. It rode rough like something was out of time. So i figured out that on a cold start say after over night, it would run fine but after it was hot, it would do this.
So i ran the codes and got misfire on cyl 3. So to trouble shoot i tested battery and starter, everything checked out. No problems there. Then on to spark plugs and wires. They were in rough shape so i replaced all 6 spark plugs and wires. Used NGK platinum plugs dual tip. and NGK wires part#4412. Fired it up and ran smooth, took the car for a test drive and about 2 miles down the road, my CEL flashed and came on and it misfired again while driving.
Now when i got home, i checked under the hood again and my engine oil had disappeared. I check fluids once a week to once every two weeks. About every time i fill up for gas. My oil label was just slightly below full a week an a half prior and now it was VERY low. Probably a quart left in the tank.
Panic'd and checked all over the place. No oil leaks. I park in the same place very night. And its CLEAN. SO i bought some oil and filled up jus to get something in there but since the test drive i have left it off and haven't turned it on for fear of doing more damage.

At this point I'm assuming its a fuel injector problem or a coil pack(Ignition coil)?
I just need some thoughts, and wondering if anyone else has had this problem.

Thanks



Here are pics of the old and new spark plugs and my oil dipstick
http://imgur.com/oeNPrlH