2000 Chevy Astro ABS Light, ck engine light come on engine

I noticed this past winter after snow would melt on vehicle that set overnight, my van would have a hard time starting.

During the spring the vehicle would be running fine then if it was raining after a little bit, the ABS & Check Engine lights would come on, and the speedometer would start jumping and van would run rough like it was missing.

I replaced the plugs and wires, distributor, rotor button, etc.

The van still won't start after raining and is dying when running wet, battery light comes on when accelerating. I put a new battery in and still doing the same. I had the altenator checked and tested to be a good altenator. Didn't know where to go next.