The reason for angle of rotation torquing is that the force necessary for continued rotation reduces once the metal goes into non-elastic deformation. In other words during normal torquing the bolt is stretched elastically (if released it would return to its exact length and diameter). In this case aditional tightening will require extra force linearly.

During angle of rotation torquing the bolt goes beyong elastic deformation and stretches (it gets longer and smaller in diameter). Once this point is reached the torque necessary for deformation goes down; thus the actual stretch can't be measured by torque.

Anyway, I would back the torque off to less than the second step and start over. Years ago we retorqued all head gaskets after getting them hot. We no longer have to do this because of better gasket materials (they say). I would have no problem with retorqing though. I believe it will be better than if you had done it right in the first place.

BTW, I say to back it off to below the second level because torquing should be done with a continuous rotation. You should not stop close to the final level as the torque necessary to continue torquing (dynamic friction) is much less than the torque it will take to get it moving again (static friction). You can check this by torquing a bolt to say 50 ftlbs and then use your torque wrench to loosen the bolt. The torque will be much higher to get it moving. You can also see it by going to 50 and stopping and then watching what torque it takes to start retightening.