98 3.0l- Has new starter, alternator, battery all got tested at orielys and they work. New fuel pump, it works

Couple weeks ago my rpms on long drives when in neutral would waver between 1-3 and slowly get closer to normal and steady out- never tried to die or nothing even at a stop just wavered and went back to norm.

I have wiring issue from my starter to ignition so I use power probe to start my truck now (took to a mechanic and he gave me this advice and has been working for months)

Drove two days ago 45 mins into town and back. Totally normal. Next day I got to start her up and the starter is trying, battery is at 12.5, but just won’t turn over. I checked all my fuses- replaced some bc my dome lights and powered windows been going out. Made no difference- gonna replace my camshaft sensor bc idk that or my crankshaft.

That’s why I’m here asking y’all think I should I do or what y’all think it could be. Pls and thank tou