The majority of airlines will ask to see a visa or onward travel within a specified timeframe, especially when it comes to VoA & Visa Exempt because if a person or people are denied entry and do not have a ticket out of Thailand they have to foot the bill.
For work you will require a degree, without one you won't meet the requirements for any type of job. And the lost of requirements you and your employer must meet is quite long for a non-b and/or work permit.
As for visa options, you have non-O/OA retirement, DTV, Non-O marriage (when you're actually married), LTR, Elite Visa, I mean heck you could even get an ED-Visa of you really wanted...
Stating which one is best for you is impossible with the information you gave, it all entirely depends on your circumstances. And all of them have upsides and downsides, if you want more accurate information, you'll need to give us more information.
You're through entry in less than 5 mins and through exit in less than a minute if you're from one of the countries that can go through the automatic gates (you just have to submit your MDAC before
Yes, if you leave on the 19th and return on the 19th you will be given another 90 day stamp. However, you should search the forum prior to leaving and some of the Laos borders do not allow same day return (although, this may only be enforced with visa exemption border runs, I'm not 100% sure, so better to research)
The limit has been removed, however you should note as always, it's down to the immigration officer you're facing at the time and you're not guaranteed entry