Whichever one you choose will have zero impact on who CIS will process your application. I would try adjustment applicant.

About a year. But you can check the USCIS website. Considering that it takes about 30 seconds to process the application, you be the judge.

It seems to me that you could apply for OPT. Generally getting a second work permit is a problem. But OPT is a status, it's not a work permit.

You can check the CIS website for processing times, but I would estimate one year.

If you have no proof you are in valid status and authorized to work, I do not see how you can complete an i-9.

CIS can process both the 751 and N-400 at the same time, make sure they know at the local office. Yes, your wife should be there, and if there is...

The employer is not required to allow you to continue working without a work permit.

If the tax returns show the required income, there is no need for any joint sponsor. Correct the tax return if it was filed without the correct...

It does not seem likely there will be any changes that will affect your decision whether to take the new job.

If the new h1b is granted you are expected to begin working for the new employer immediately.