1. 2,000 baht is visa entry for 90 days - then you must extend for 1,900 baht with proof of financials (2 months in Thai account or 12 months of pension payments into Thai account (in your name only accounts).
2. (3) No. The US Embassy will not confirm pension income - so we only have option of 12 months of 65k or more payments into Thai bank account for income method. You must have money in Thailand or coming into Thailand for in country extensions of stay.
3. (4) there is no option to extend 90 days without meeting financial requirements.