Are you actually using the 12v for anything?
You could just use 4 AA batteries to get up to 6v (for non-rechargeable alkaline) or ~4.4...5.2v (if using rechargeable batteries) and just use a 5v regulator with very low dropout voltage or a buck-boost 5v regulator
For example AP2202K :
https://www.digikey.com/en/products/detail/diodes-incorporated/AP2202K-ADJTRG1/4470808It's adjustable, accepts up to 13.2v input, outputs up to 150mA, and a maximum dropout voltage of 0.35v at 150mA (0.15v at 50mA) - even with 4 rechargeable AA batteries, you'll have around 4.5v on output which should be good enough, your microcontroller will work just fine even with less.
AP2210K -
https://www.digikey.com/en/products/detail/diodes-incorporated/AP2210K-ADJTRG1/4470821 - goes to 300mA, maximum dropout voltage is higher, but at low output currents it will be about the same as previous regulator
Alternatively, you could use a couple 18650 lithium cells in series and a charger that can charge them ... this way you're guaranteed to have more than 5v on input and long battery life.
for example MP2672A -
https://www.digikey.com/en/products/detail/monolithic-power-systems-inc/mp2672agd-0000-z/13572801 - can take in 5v from a USB port, boost it up to 8.4v and charge the cells, and also supply this voltage while charging the batteries on a "system out" pin, and when the 5v is disconnected, the battery is connected automatically to system out pin, so you can put your 5v regulator on that pin
for your negative voltages you could use a charge pump in inverting configuration, like LM2776 for max 200mA -
https://www.digikey.com/en/products/detail/texas-instruments/LM2776DBVR/5356685 - or LM2660 if 100mA is enough
https://www.digikey.com/en/products/detail/texas-instruments/LM2660MX-NOPB/366876 or TPS60403 if 60mA is enough :
https://www.digikey.com/en/products/detail/texas-instruments/TPS60403DBVR/1672064