You need to go to immigration and fix the entry stamp first, the officer probably had his stamper on the wrong month. After that, apply for the extension.
No, if it says under consideration then that's normal. All covid extensions you have to go back for, some are at 15 days others are at 30 days depending on the office. You don't have to pay anything when you go back and it's always approved.
Pol Lt Gen Surachate, his English name is "Big Joke". He used to be the commander of the thai immigration police, now he heads up the country's anti corruption investigations.