Your original question about pain from the crest of the hip is a tell-tale for having a locked up sacroiliac joint, in conjunction with a l3-l5 issue in conjunction with the hips locked in extension.  This can lead to very serious problems.  I know because I suffered the exact same thing.  The pain while sitting is basically an elevation of the same condition, meaning its getting worse.  High level athletes are able to perform with similiar or worse conditions because they do so many things.  You are in good shape, and doing a lot of right things, so you are able to be functional in this condition, but as you grow older it will catch up with you. You have to find a good chiropractor that will work with you to unlock the sacroiliac joint and l3-5 out, you cannot do that on your own.  A very good massage therapist may be able to unlock them but that is rare.  When you have that level of fault the muscles will not relax via stretching, its part of the protection mechanism.  They have to be massaged lose.  Once your back is straightened, and your hips and sacroiliac is unlocked you can begin to work on a few areas.  The first is the hip flexors.  they need to be stretched and lacrossed, to do that get 4 balls and tape them in a pyramid structure.  the second area is the psoas.  the third is with hip mobility, put a foot up on a counter and try to get that foots knee outside the shoulder.  As to your calfs being sore, I suggest listening to the joe rogan experience episode with Kelly, the walking/running part will give you insight as to the problems cause.

As kelly has stated in other videos, the key to relief is though giving the damaged tissues slack.  One area that has helped me with lower back pain is smashing my hip flexors.  This is difficult to do but I found a way to do it that makes it a lot easier.  Start by finding a normal sized chair and putting the left foot on the chair, then take your left elbow/forearm and dig it into the crease between the hip and quad, it should hurt.  The mashing technique that works best for me is to try to move the muscles from the inside to the outside or working outwards, starting in the deep crease of the hip and working to the knee.  Then repeat with the right side. If a person is experiencing a moderate to severe amount of lower back pain then one side or both hip flexors should be tender to work on.  The next thing to do is put the left foot back on the chair, and in a half squat try to get the left knee out and past the left shoulder.  Repeat with the right foot/leg/shoulder.    Your back pain should dramatically decrease.