It depends on all of the facts. The details make a difference.

It depends on his prior travel history. Certainly the longer he is out, the more likely he faces a denial. Under 180 days may be safe depending on...

You will not be denied an H1b based on any immigrant visa application.

If you have an F2 visa which is multiple entry, you can come in and out of the U.S. as many times as you like, including daily.

You cannot have both statuses at the same time, you are one or the other.

You could try calling customer service to find out.

Instead of doing that, why don't you have the second employer file for concurrent employment?

Yes. if the new program is subject to 212(e), then you will be subject to 212(e).

It is permissible generally to send photocopies to USCIS even including signatures.

Check the instructions. Sometimes CIS wants you to say "n/a" which means "not applicable" and other times they would prefer you to write "none" or...