No it shouldn’t be a problem based on length of overstay.

Yes you may share the nature of your concern here.

May be worthwhile to consult with an attorney to explore your options.

You can attempt to resubmit the missing document to USCIS or wait until decision.

The addresses you found are correct.

It begins when the visa becomes available.

Yes once he enters the US as a LPR.

An adult married child of a USC will take about 14-15 years until the visa becomes available.

You should consult with an attorney to explore other options as you must have a qualifying relationship for vawa.

The pending application alone does not give one status.