This was pretty much May's plan all along: hold her nerve with the deal she'd negotiated, threaten pro-EU MPs with No Deal and anti-EU MPs with no Brexit or a long delay, then get enough on board to get it through parliament. Problem is that she's lost control of the situation.
JRM can talk about getting this deal through parliament to ensure he gets some sort of Brexit and then working on it from there, but I doubt the EU would want to renegotiate anything in the withdrawal agreement once it has been ratified. The future relationship has yet to be negotiated though and it depends Parliament approving the withdrawal agreement first, which won't happen.