H&C not a great option. Processing is many decades at the moment, doesn’t prevent removal and is one of the programs that is at high risk for major chances since it is no longer functional.
There is no other option for him. One of pitfalls of Bill C2 according to advocacy groups is that it leave people from ADR/TDR countries in legal limbo in Canada.
Apply for Judicial Review. If you carefully read the Bill C-12 it is only applicable to cases that are not referred to IRB. It does not give IRCC the power to redetermine the cases that are already referred. It cannot be used like a time machine. A new law is presumed not to strip away rights already acquired under the old law, even if Parliament uses prospective language Dikranian v. Quebec (Attorney General), 2005 SCC 73.