NO... you can extend your visa up until and including the day of expiration without a "fastlane fee"... the expiration date on your of the visa stamp in your passport is the last day of extension without fee ... OMT.. check the holiday calendar for the Philippines to make sure they are not closed when you plan to extend...
You do not have to renew for another 2 months. You can extend on a monthly basis. The prices are not the same.
More easy is before departure to apply for a visa in your home country which is valid for 59 days. So it will save you the hassle to get an extension while in the PH.
Yes, you can get it through the embassy. Another option through a consulate, if available in your country.
No, the 1st extension is for 29 days (takes you to 59 days in country total, leaving the 60th day is a mistake that will cost another extension) No, the 60th day will require a 1 or 2 month extension. (there are no 1 day or 59 day extensions). After the 2nd extension the options are 1, 2, or 6 months. 99.9999% of visitors to Dumaguete will be staying Much closer to the Duma BI office which is likely Much easier to deal with than a Philippine Embassy/Consulate in another country.