Long story short, my car was a victim of “.

Long story short, my car was a victim of “phase separation” over 3 years ago. Ever since I replaced the fuel filter – which took care of most of the problem – there’s been some drag in acceleration. I’ve replaced a ton of parts. Some were proven to be sloshed and some power was restored – TPS, cam and/or crank sensors, oxygen sensor, and every part in the fuel system that the pure ethanol touched – most weren’t. Now the accessories are all getting weaker. The factory alternator gave out a year ago. I had to have its replacement replaced last month as the accessories were really weak at the time – lights flickering, etc. But the accessories are still a little weak, and the pedal still has some hesitation/resistance through all this. The accessories are getting so bad my power windows are slow to roll up when the car is off, so that tells me at least one of three things is sloshed – battery, battery cables, or ignition switch. The one that would make the most sense is the battery. But I had that tested a couple months ago and Autozone said it was fine. I installed the current battery right after this phase separation happened at 70k miles. It just wrecked whatever was left of the factory battery. The car now has 106k miles on it. So this replacement battery has over 35k miles and 3 ½ years on it. The new alternator squeals a little FYI. But the dealer said it's fine.
Last week I had another dealer test the resistance in my ignition system. They said it read 0 ohms, so that pretty much tells me the cables are ok. I’ve seen the theory that it’s good or necessary to change a battery when you change an alternator. Is there any truth to that? I don’t know, maybe the battery and alternator aren’t getting along. Any insight and direction would be fantastic.