96 3.8 Hard Starting/Rough Running Battery Light On

I'm putting my van back on the road after sitting for 1yr and it is hard to start then once it starts it runs rough. Once it runs for a few minutes it will smooth out, but if I shut it off then restart it , it does the same thing. I replaced the fuel filter and checked the fuel pressure which looks strange. It is KOEO 20lbs which I know is low, but when I get it started it bounces from 25-35. I pulled the vacuum line off the regulator and it made no difference. Fuel pump bad? The other problem is with the battery light, when I was letting it run it would come on then go out. I got my meter out and started checking things and I have 14.3-6 when running, 12.3 when off. I charged the battery before I put it back in so I wouldn't kill the alternator. Any ideas. Thanks

I would check and clean all the battery connections and verify good connection to the chasis.
Otherwise, you may need a new battery.
The battery light is an indication that a voltage is being sensed as too low, which only takes 1 poor connection, or defective battery, or defective alternator.

Low voltage will cause the engine to run rough, can cause fuel pump issues, etc.