Your extension is only issued until your passport ending date. It is not dated past your passport expire date. That is why. If your passport expires in August then your extension is only dated until August, not April.
not in Bangkok it won't. Other provinces yes, but Bangkok requires a certificate of residency, which you can only get after you've done at least one 90 day report.
It is cheaper for seven months to get the multi-entry tourist visa in your home country. With just leaving and returning to Thailand, you can stay almost 9 full months, covering the seven months needed.
You have to personally have a legal licensed business, or work for someone with a legal licensed business. You also will need your most recent income tax filing. Most everyone contributing to Facebook doesn't have an actual licensed business, and pay income taxes on any money they might make writing on Facebook. It has to be a legitimate legal job, or business that pays a wage, or makes money.
try to keep up with changes. As of the first of the year companies are getting busted for using proxies. Now you show that wages are also being paid, not just social security. Times change, as do requirements.
You are overlooking one very important detail about getting a work permit. For a company, even your own, to sponsor your work permit they must have at least bt2million in registered capital, and hire, and pay, at least 4 Thai employees. For a regular business setup there are no exceptions to this. If it is a business setup with your wife, and you are on a marriage visa extension then these requirements are cut in half, to bt1million in registered capital, and just 2 Thai employees you pay wages and social security on. The age of proxy workers ended this year. If you no longer have the bt400,000 for your marriage visa extension I doubt if your company has the required amount of registered capital for a work permit. The cheapest option would be to borrow the bt400,000 for the three months you would need it, as there is no requirement as to where that money came from. Only that it is in your account for at least two months before you apply, and in some provinces for the under consideration time period before you get your yearly stamp. If your wife's family can't loan you the money, then your wife will know a loan shark that can. It is not that expensive to do.