Too bad you cut off all that...they make repair rings that you could have used and not be in this situation. One type is hinged and would have fit in the notch the old one fit into, others are just a ring that can be bolted down to hold the flange bolts. How much height of straight pipe have you got to work with? If it's enough, you can pick up an inside pipe cutter (essentially a small circular saw on a shaft) to cut off enough, then glue on a coupling, a short piece of pipe, and a new flange. You could try to cut vertical notches in the flange, then trying to peel it off. If the joint is well done, it will damage the vertical piece of pipe, but maybe not enough to prevent a decent seal. If you have access or can gain it from underneath, you could maybe cut out more if required.