i have to say that you have not proved where the symptoms come from and the suggestions about treatment are moot. you have not shown in the symptoms are coming from the hip, Wikipedia reference-linkSIJ, or lumbar spine. if the lumbar spine is tight then any of those structures could be too.

take an irritating movement and test it. for example, trunk rotate to cause irritation and have the pt stop just into the onset of symptoms. then, use unloading to see if it changes the pain. first, unload the hip (you will be kneeling next to the pt). put one hand on the anterior superior iliac spine and one on the ischeal tuberosity. push upward. if this decreases the pain then it is perhaps coming from the hip (which has been shown to radiate pain as far away as the foot in research studies). likewise, unload around the trunk which usually requires wrapping your arms around the lower rib cage. if this helps but the hip unload didn't then perhaps it means the pain is coming from lumbar or SIJ.

for SIJ testing Laslett 2005 (good testing cluster since any one test is a poor indicator).

if you aren't sure where it is coming from and the patient is tight mobilize one area: hip, lumbar spine, or SIJ. then retest him (standing trunk rotation sounds like a good one - remember, the hip is rotating with this). whatever helps decrease the pain go with it.

as for the previous lumbar treatment you haven't mentioned a hip flexor/iliopsoas stretch. i would include that if he is tight as well as a quad stretch. they are often overlooked.