Reusing bootleg CTR-003 battery packs (Nintendo 3DS)

The batteries in question

Hi, bit of a noob here. A friend bought two replacement batteries for his 3DS and the middle pin isn't wired properly, so the console doesn't boot. However, they still seem to hold juice just fine and I want to reuse them for a Bluetooth speaker project.

They would power an ESP32, a couple of 3W max amps and speakers.

My questions:

• Are they too small for this project? How much battery life can I expect? If they're too small I have an old 10.000mah powerbank I can recycle (it charges only to 80%)
• I'm not sure I trust the integrated protections (if they're present!) and I want to get a charge controller with security features. Can I directly connect it to the battery packs or do I need to remove the existing PCB? Do I need one controller or two?
• I'm currently using a MAX98357A DAC+AMP to test the setup, sending data from the ESP32 with I2S and connecting the amp directly to the ESP's ground pin. I do need to change the wiring setup to have this all work right?