Regarding his previous B1/B2 travel history to the U.S., there shouldn't be an issue with further travel while his case is in administrative processing. Although there's a slight possibility of being turned away at the airport, Customs and Border Protection usually treats spouses of U.S. citizens with consideration.

To avoid potential travel hassles, your son-in-law can clear U.S. immigration at Dublin Airport, which offers a more convenient option.

Answer 1 : While there's no official answer, in our experience, you can transfer your H-1B even before October 1st when it's approved in August. No need for pay stubs from the previous employer, based on our experience.

Answer 2: If you never joined the employer, you won't have pay stubs, which is acceptable. Even if you join and leave the employer on October 1st without a paycheck, that's fine too.

Answer 3: Multiple employers are generally allowed unless they're connected or conspiring to manipulate the lottery, which is not allowed.

It is better to address these issues proactively rather than waiting for a Request for Evidence (RFE). While it's advisable to be prepared in advance, if an RFE introduces new concerns, you'll need to address them. However, this doesn't imply that the affidavits you prepared several months earlier will suddenly become problematic. If the affidavits are relatively recent, say one or two years old, it wouldn't be a problem.

Consider this scenario: If you had a spelling name issue and obtained one or two affidavits explaining it, and then the RFE raises this issue along with another one, you can simply provide supplementary documentation. The documentation you've already provided doesn't lose its validity just because the government posed additional questions.

In our practice, we only resort to preparing for a DNA test if it becomes the last resort because it can be quite expensive. I'm not certain about the exact cost, but we typically wait until the government explicitly asks for it.