Powering the esp12 with an UA78M33CDCY voltage regulator
Have a look at the datasheet (Page 5) the 3.45v is still within the margin of error of the output voltage. If such small voltage changes are an issue for you, you may want to look for another more precise regulator. Its kinda difficult to tell if you can run the esp12 with more than 3.3v because there is no absolute max. rating in the datasheet.