You can always solve the domicile issue by searching for jobs, finding an apartment etc. Your tax returns are all you need to show you've been filing your taxes. You need to show the "total income" from the past three years when the time comes. That's going to be zero, for all three years. If you are still working abroad, then zero will also be your current income, so you'll need a qualified joint sponsor, unless you come back and go to work in the USA, or have significant liquid assets. (minimum of 3 times the income shortfall, which in your case is the full income requirement times 3).