IF you can get the left crank arm off, and IF you can loosen the right fixed cup, this should not be too difficult.

1. Remove the left side crank and adjustable cup. Remove the right side bearing/s.

2. Now unscrew the right side cup and you should be able to pull out the right_side_crank/chainring/axle all in one piece. Now you just have to get the axle removed from the crank.

3. Put your big_ass_adjustable wrench, or axle vise blocks, under the crank arm. If your chainrings get in the way you'll have to figure out how to protect them.

4. Now, put this whole business in a vise (but not tight) with the free end of the axle pointing down.

5. With a large diameter drift punch and hammer (a dead blow hammer would be perfect), drive the axle
out of the crank arm. You just want to make sure you protect the bolt hole in the end of the axle. I'd put a short bolt, with a washer in it and screw it right down tight. That bolt would have to have a small enough diameter head to clear the square hole in the crank arm.

Assuming this all works, you just need a new crankarm (if you can get just a right side). Good luck!