@Sam Hopi 1040-NR is per individual i.e. each NRA submits one 1040-NR, you are effectively taxed as a single individual -- you file as "Married".
I suspect you are talking about form 8812 -- please see this document at www.irs.gov and search for schedule 8812. I think either NRA -- J1 or J2 can file for this -- it is obviously income bound.
About you question on schedule-C , even though you are an exempt person for two years , you do not come under FICA/SECA exception -- you still file schedule-SE. You can avoid paying into Social Security if Brazil has a totalization agreement with the USA ( it probably does ). You then would generally pay into one and have a certificate of participation from the other.
I still think . you should use the services of a tax professional.
Also you said you are enquiring about tax year 2023, but you arrived in 2022 -- how did you file 2022 return ?
Is there more I can do for you?
pk
