Why does my home's power fade and surge when I plug things in?
Call your UTILITY now on their EMERGENCY NUMBER

Your service neutral is going bad.  This is a power outage even though it doesn't appear so -- the fluctuations in light and heat you see are because the 0V reference mark for all your 120V outlets is no longer acting as such, resulting in outlets getting higher and lower voltages depending on what else is plugged in.  There's a good chance some things will eventually catch on fire if you keep this up

And please put properly rated breakers back in, so you aren't playing with fire for any longer than you already have been!  Whoever told you to do what you did with your breakers knows nothing about electricity, and should not be treated as a reliable source of electrical advice ever again!