Well, you can't do anything without a surgeon. And you have time (without pain) to get the opinions of several. Your pain specialist recognizes that both spondylolisthesis and buldging disc are progressive conditions which are now compressing nerves to the thighs. The combination may make the stenosis severe, but you you need a stage on the spondylolisthesis. There are minimally invasive procedures for each condition that can increase the space for the spinal nerves. If the spondy is caused by a fractured bone there may be remedy short of fusion.