In the GPIO map (https://www.olimex.com/Products/IoT/ESP32/ESP32-DevKit-LiPo/resources/ESP32-DevKit-Lipo-GPIOs.png) it says it is GPI34 but in the schematic (https://github.com/OLIMEX/ESP32-DevKit-LiPo/blob/master/HARDWARE/ESP32-DevKit-LiPo-Rev.B/ESP32-DevKit-Lipo_Rev_B.pdf) it says it is GPI35. Which one is it?
Also in the GPIO map it says that BAT_SENS_E1 should be closed, but I'm guessing reading the schematic that BAT_PWR_E1 also should be closed, right?
Schematic is always right. GPI35 it is for the battery measurement.
Yes, closing both BAT_PWR_E1 and BAT_SENS_E1 is required to enable battery measurement.
It is very likely you'd also need external power sense (to detect when board get powered by external source or battery). It is GPI39 and requires soldering together the pads of jumper PWR_SENS_E1.