The final issue has been solved! We had a bad temperature sensor and controller. If you see your boiler overheating and boiling over even though the temperature is lower than the boiling point, you have a bad sensor or controller! Replace them immediately!
The parts I had to use are listed below, and it only cost me $62 at a local dealer.
Part# 5958 TEMP WELL, TS LOVE CONTROLLER
Part# 727 KIT,THERMISTOR W/ BRASS PROBE & TAPE