Possible SMC failure - no battery indicator, no backlight, max fan spe

Hello! I purchased this MBP from my local marketplace in August 2023. It had a bad HDD cable, so I replaced that and swapped in an SSD. It worked fine for a couple of months, then I stopped using it. I recently took it out of my drawer to test something, and surprise - no power. I tried booting it without the baterry, ram, ssd, literally everything. It would only ocassionally boot to macos, work for a few minutes, then power off and not boot for another hour.

Yesterday I took a look at it again and I tried powering it with only the magsafe cable attached and it worked. I have to hold the power button for 10sec(without charger) and for another 10sec(with the charger) and it boots. If the baterry is connected, it won't boot at all. But if I plug in the baterry whilst the macbook is on, then unplug the charger, it stays on only on the batterry. Problem is, the batterry indicator has dissapeared. I also get no white light, the keyboard backlight doesnt work, fans spin up at max speeds all the time.

I tried ALL the resets available, but to no avail.

Please help me. Thank you