A thought: given that he's got a minority administration anyway, does Johnson NEED to the placate DUP? Indeed does he need to be constrained by Maybot's infamous 'Red Lines' either?
Ignore the former, compromise on the latter, get a different deal & fight an election on it?

Farage & his fellow travellers can & will yell but if it takes the UK out and, particularly if Johnson wins a large mandate for his deal, the BP threat to his right is neutered and there's nowt the frog-faced fucker can do about it!