Hopefully, Ethiopians who have experienced this will assist you. You could also go to nearest Ethiopian mission or Embassy for a face-to-face. Why was GC application denied though?
This specific directive is to embassies which are part of DOS. USCIS is part of DHS so this specific directive does not apply to USCIS. But who knows what might be coming for USCIS; it's wait and see.
US embassies instructed to prepare for staff reductions
https://abcnews.go.com/Politics/us-embassies-instructed-prepare-staff-reductions-sources/story?id=118755936
US citizens don't need visa to enter the US for anything so no such visa exists. Son should just enter with US passport and enroll in the final year of high school. Free in public school.
Op. I understand your frustration. Just to confirm and my apologies if you already answered this.
Your wife completed I-864 and you completed I-864A? Correct?
No need to wait 90 days. Marry and file I-130. You'll never know when the chart might jump. Especially, chart B. Choose consular processing though. If it happens she's still in status when priority becomes current she can still adjust.
Good luck
You guys can't do adjustment of status now anyways; that category is not current.
You can marry and file just the I-130 petition if you want your priority date to be earlier than waiting for next year.
When does F1 status end?
And there's no 90 day rule for DHS.