You stated "The battery wouldn't charge and we reset the BIOS and it worked. After turning the device off and on, it slowed down considerably. We checked and saw that the CPU was stuck at 0.2." Exactly HOW did you reset the BIOS? Which exact model Surface do you have?
Most Surface devices prevent you from disabling BD PROCHOT to protect you from damaging your Surface and you'd have to use a 3rd party utility which I do not recommend.
Do the Surface Diagnostics show any issues? You may need to contact official Surface Support or an approved service provider for repair/exchange. Where are you located/