First contact your attorney as collection actions are limited in some cases, i.e. they require court approval. And if you are not comfortable with SCRA then you need someone guiding you that is familiar with the "dos and don'ts".
Second, there is nothing in the Federal statute that prevents you from reporting the account past due to the CRAs. However, you may need to check state laws.
Third, the SCRA does not give the co-borrower the right to remove themselves from a legal contract. However, there are some lease exceptions in the SCRA.
The opinions expressed are mine and they are not to be taken as legal advice.