Alternator/Battery Problem.

My alternator died 2 months ago. If I tried to use the heated seats or headlights with the engine off, within seconds the battery saver would activate and the engine would crank weak. Turns out the alternator was only putting out enough to restart the engine. Replaced that with a AutoZone one, but I plan on putting a AC Delco In later on. But everything seems under powered. Idling voltage Is at 13.8. When It first starts It's around 14.5 then slowly drops to 13.8 with nothing but the engine on. When I full field the alt from my scan tool the dash gets brighter, the blower motor speeds up, the wipers/windows don't slow down, everything performs better. When It's full fielded voltage Is at 15V and that's Idling at 600 rpm. I had Issues last year with the battery current sensor I redid the terminals and couldn't remember which cable the sensor went on. I finally got It figured out and the code for that hasn't come back. I routed both positive cables through the sensor like all said. But Idk If the battery Is the problem or the PCM/current sensor not telling the alternator to output more. I always thought the dash was kinda dim as I drive alot at night. When I replaced the alt I tested the battery 3 times and It passed every time as It's less than a year old. Deka brand battery. Im not having any starting problems but I don't like how everything Is slow and dim. I also did the big three last year. I don't have anything aftermarket/sound system. Think maybe I need a bigger battery with more reserve/possibly a AGM? Thanks.