Loosing his seat means his days are pretty much numbered, despite what DUP members are saying publicly. Holding onto his seat was a chance to try and regain ground and fight back against the internal factions looking to get rid of him, now that he has failed I can't see any other way out.

As for having no influence in Westminster it all depended on the Tory numbers. If the Tories had have been just shy of a majority they probably would have done a deal with the DUP to leave the norths finances alone (or at least relativity unscathed) in return for support. As it stands the North is likely to loose a lot of money.