Engine having issues turning over. 196,000km?

In order to grasp the full story I'll start from the beginning. A couple months ago is when I first notice my truck having issues starting, when the engine was cold it seemed to take awhile to turn over, and when it finally started to catch, it would be a very weak start (usually this wouldn't happen when the engine was warm). One morning, it started rough per usual, however this time the abs light came on and stayed on for a block or two (the light hasn't come on since). I went on a hunting trip and most of the mornings when I started it, it would turnover weak and then bog down almost to the point of stalling (after the trip, this didn't happen again). A week or so went by and my engine light came on. I looked up online what the probable causes and everything pointed towards the MAF sensor. I disconnected the battery and preceded to unplug the sensor so I could see what I was dealing with. This caused my engine light to turn off. I bought the proper security torx set to get the sensor off and then sprayed it with MAF cleaner. The next day I brought it into my mechanic, he was unable to read the codes because I reset it by unplugging the sensor. He replaced the fuel filter. After that, my truck seemed to start fine with no weak starts, this lasted about 3-4 weeks until my engine light came back on and the starts became weak once again. I was told before that I may had cleared the codes by disconnecting the battery, however this time I unplugged the battery and reconnected it right away, turned over the truck and the light was still on. I then disconnected battery, unplugged MAF sensor, reconnected battery, turned on truck and the light was off. I went to an auto-wrecker and bought a used MAF sensor. I replaced my old one, however the negative battery connector broke. Replaced that and now its a strong connection. For about a week my truck ran and started well, with no issues. My engine light came back on. I took the 'new' MAF sensor out and brought it back to the wrecker, and put the old one back in. This brings me to where I am now. Engine light is off, and my truck is turning-over weak. Any ideas on what the cause could be would be greatly appreciated.

Also, thought I'd mention that about a year ago my daytime running light module died, causing my lights to stay on. The next day my battery was completely dead and I had to be jump started. Would this cause a dead battery cell, leading to future problems?

Thank you.