U.S. government is absolutely hostile to expats, tourists, and (legal) immigrants. Try visiting a US Embassy or applying for a tourist or marriage visa for your SO, or requesting citizen services.
The China visa office is not at the embassy, it is at an office building in Petchaburi Road as you said. Not near airports but close to MRT stop. Doubt any nearby hostel but many condos and there is a hotel. If you prefer a hostel try Photohostel in Chinatown. Nice clean place, European owner see that his staff takes care of you. One trip on MRT to visa center.
No. They will show you insurance, but what it will pay if you’re seriously ill, even if it’s not excluded due to being deemed a pre-existing condition, will be not much more than your annual premium. Might as well self insured.
staff at US embassy were never rude to me but I interpret their reducing services and long appointment times as anti-expat, plus the plethora of us whose partners cannot get tourist visas in spite of good jobs, passport full of stamps etc.