is the best agent. You don't pay her until your license is in your hand. She will meet you at license office to help with paperwork, translate instructions for your eye and reaction tests. 100% legit. Make sure you have your motorcycle endorsement on your IDP if you want motorbike license. If not, go take a course. Thailand IS NOT the place to learn on vacation.
As long as you want. Have someone you trust take care of your mail, etc. If your home is now thailand and you're disabled, even easier. Keep in contact with your attorney and doctor.
I've been paying for extra luggage every time I come back. Move important stuff every trip. Far cheaper and not having to deal with border customs bribes, excessive import fees, and "disappearing" shipments. You can get pretty much anything. Depending on your size and if you like certain brands, bring with you as thais are small. I personally have a hard time finding clothes that fit how I like and a couple brands so I bring some stuff with me. Electronics buy here.