Arduino for STM32

F103C8 does not have DAC (analog output), only PWM so what you get is correct.
If you want analog output you need MCU with DAC or external DAC.

Looks like regulator got fried.

As .rpv wrote, this 60mA current draw has to come from something else than MCU.
I have F401 anf F411 black pills and they draw about 20mA.
And some F103 Bluepills which draw about 30mA.

To power RTC connect 3V battery to VBAT and GND. To use RTC with VBAT power, you need to set clock source to LSE before starting RTC.

ad.2. https://github.com/stm32duino/STM32RTC

You can use Hardware Timer to generate time base interrupts:
https://github.com/stm32duino/wiki/wiki ... er-library

Adafruit library works only with STM32 core.

Just change
#define PIN 6
to
#define PIN PA10

But Adafruit library isn't optimized for STMs and on F103 it takes over 1ms to send data for 8 LEDs (about 280-300us on Arduino UNO/nano).

Probably you try to access "Serial" in your library which isn't initialized and program hangs. To see if program hangs I use simple test with LED: turn LED on before tft.begin(), turn it off after. If you use Serial to output any data, use it in "if" if(Serial) Serial.print("...

in STM core:
GPIOB->ODR = x;