Your filing date is June 15, but any tax due must still be paid by April 15. The bona fide residence test does not dictate the filing date when you've moved late in the year; it affects your ability to use the foreign earned income exclusion, which probably won't apply to you.
You will be filing pretty much as you always have, which I assume is married filing separately. Any US social security you received after you moved to the UK is only taxable in the UK. The tax treaty helps us regular folks very little, and without debating the detail or interpretation of said treaty, for simplicity's sake just assume that other income is taxable in the US regardless of whether it's taxed here. You can take a tax credit as appropriate.
The feds make it nigh onto impossible for us to e-file. I've paper filed for the 2 tax years since I've been back. The post mark date s fine, just as it is in the US; even with Airsure you probably won't have a clue when the IRS receives your return - if you want a bit more comfort, bite the bullet and pay for FedEx or UPS.
If you haven't worked since you returned, your situation is likely more straightforward than you think. Your state tax return is likely to be more complicated; mine definitely was in VA for that first year.
