Declaration of a State of Emergency -- can President Obama issue one to prevent default?

[Nuclear Unicorn]

35. What underlying violation of law could occur by congress exercise its constitutional power?

You cannot force congress to vote on/pass laws anymore than they can force a president to sign the laws they pass. There is a process for determining the language of bills. Once the language is settled then the bills receive their votes in the respective chambers, go to conference committee etc. That is the constitutional process and the Constitution trumps the National Emergencies Act. None of the constitutionally ordained legislative process violates the law even if federal expenditures slam face-first into the debt ceiling.

Once the debt ceiling is reached the federal government is legally obligated to stop incurring new debt (it still has plenty of revenue to pay debt service and a fair amount left over for operational costs). That's not a violation of law, that's obedience to the law. If the chips fall poorly on the economy, oh well, it wouldn't be the first -- or last -- time the government did something stupid. The remediation for stupid isn't imposing government by presidential decree the solution is to GOTV.