1) should US military bases:
a) become military bases of Exstatia,
b) remain as US military bases and function like those in Germany, Japan, Korea, etc.
c) be disbanded with all personnel and equipment being transported back to the US,
The federal government should chose: with exstatia permission, it may maintain the base as their own OR it may cede the base to Exstatia (in which case it should include the base among the federal infrastructures for which Exstatia is expected to pay), OR it may dismantle the base (in which case it's not infrastructure Exstatia has to pay for.
2) Does the ownership of nuclear weapons that have been stockpiled within Exstatia:
b) remain with the US,
3) should members of the US armed forces who recognised Exstatia as their home state before secession:
c) be given the option to continue serving or to be released from duty,
4) which of the following options should those who had identified Exstatia as their home state before secession have:
a) to become dual citizens of Exstatia and the US,
America recognizes dual citizenship, therefore, it should acknowledge it in the case of Exstatia.
Besides which, let go of all the juicy nationality-based taxation? Puh-leeze.
5) How much of the US's national debt should be transferred to Exstatia:
b) an amount related to assets of the US government in Exstatia,
d) other
Ideally, Exstatia should take on any federal debt linked to assets that end up in Exstatian possession, as well as a share of the non-asset-based debt based on their population weight.
This assume that such debt can be calculated precisely. This may be highly unlikely.
Failing that, Exstatia should get a share of the debt based on two chief elements
1)Market value of assets left in Exstatian possession (compared to the total market value of all federal assets prior)
2)Demographic weight of Exstatia in the union.
I won't really speculate as to the last three questions as these are highly dependent on the specific state, other than to note that Exstatia would probably greatly expand its own government to take over all the jobs formerly handled by federal people.