, OP should be able to apply for Non-O dependent on Non-B applicant at the same time at the embassy/consulate in another country. What you are talking is when applying Non-O dependent to a foreigner with permission of stay (Non-B, Non-ED, etc) at the local immigration office INSIDE Thailand.
If you can access TM30, just submit a new one with a check-out date open or long enough, for example as same as your extension. Some offices don't accept if the checkout date is filled with the date already has passed. You need to check with them.
You can send your friend for you to the local immigration office to do a 90-day report in person. A 90-day report can be done by your representative with your proper documents including your original passport without power of attorney or any special papers.
A re-entry permit wouldn't give you any additional days to your current stamp. It is only valid as same as your current stamp. If your current stamp expires when you want to go back to Thailand, a re-entry stamp does not do any trick.
All you can do is show your eVisa PDF at passport control and ask if they let you enter on visa-exempt instead.
Still, the approval of your entry on what status is at the discretion of the immigration officer. If they say no, you will enter on Non-B and get a re-entry permit when you travel again.
Better not attempt to enter on visa-exempt by hiding your issued eVisa. no one knows whether it works in your case or not. In the very worst case, you are stamped in on visa-exempt and your eVisa gets voided.