I have never heard of a doctor removing someone from plaquinel to put them on methotrexate without there being a problem with the persons reaction to MTX. Usually it is added to the plaquenil and it replaces steroids if they are being used. I am on all 3 actually and I haven't had any problems with the MTX. The first few weeks i felt bad for about 24 hours. Now I take them at night and the worst of it is over by morning. I am not saying your doctor is wrong I am just saying it is a way I have never heard of.
As far as the benlysta... I can't answer that because it really only works on certain types of patients. Only your doctor will know if you fit that category. I am sure you will come to the right decision after talking to your doctor