Not sure your background in finance and economics. But all that you have said is incorrect.
1. Sovereign default of Pakistan is highly unlikely. Most of the foreign debt is multilateral/institutional or bilateral. Nobody gains by forcing default. Everybody will work hard to reschedule or rollover the debt. They can't just go and get CDS from a counterparty.
2. Even if a sovereign default occurs, its impact is on foreign currency transactions. Domestic currency will be unaffected. Already, foreign currency is unavailable for general imports. It is being conserved for food and fuel. So, it is already a DeFacto default, but most people are not even noticing it. Except those who want to import stuff.
So, Rupees unaffected, except inflation. Dollars already unavailable for general imports. So, no difference.
3. Can't say what impact on Real estate will be as foreigners can sell but can't repatriate their earnings anyway. So, why would they sell and keep money in depreciating Rupees?
4. What happened in Afghanistan is extreme case; they are cutoff from external world. Pakistan will still be on international banking system. People can send money in from abroad. Imports will still happen, at a reduced pace.
5. "Hoarding " dollars may help in the sense that it will not depreciate compared to holding rupees. But those with a lot of rupees tend not to hoard cash.