...(Best option for EU on the other hand is to force Britain to give up their own currency and join Euro if they want to go back.)
If the value of the pound keeps going the way it has since the Brexit vote that might also be the best option for the UK, never mind the EU.
As for the DUP/Tory mash-up: according to the DUP they still haven't actually finalised any deals or agreements with the Tories, even though May has indicated otherwise. So I don't see this partnership going all that well for either of them as they can't even agree on whether or not they
agree. Plus, the Tories have been doing terrible/stupid shit like this for years before they climbed into the DUP's bed. So IMO this is all Tory.