my ipad has been shutting off randomly no matter how much its charged, and it'll turn on with "0% remaining" or 90-100%, even if it was previously dead and not turning on?

This started around 1-2 months ago, and im wondering if theres anyone that can help me. Usually, it'll also have pink/green squares or pixels when it dies and it'll turn on right after at either 0%, or 100%. (usually, it'll die almost immediately after it turns on). additionally, it charges much slower than it used to and will even die while charging, causing it to boot loop (im assuming thats what its classified as??) and it's hard to use it anymore. this is really the only device I can really draw on anymore and i'm scared it's gonna stop working sooner or later. I dont know if this is a battery related issue (which it probably is) but yeah. If it helps, the screen is severely cracked and basically shattered, but i've had a case on it since forever. I don't know what to do anymore. ive done everything I could and I can't afford to replace it/my screen at the moment.. any help? I don't know if this has/is happening to anyone else, either, since i've searched everywhere for answers and the only things i've seen are battery replacement or screen replacement. Any additional information needed? i'm also still on iOS 14.4, if that's anything useful. Ipad 8th generation, 32gb, iOS 14.4, I got it around November of 2021 maybe? I could provide a photo of it saying "0% remaining" also, if needed. Sorry if this is vague at all.