1. Call Shell. Likely it's a franchised location, but all the same they have to abide by certain Shell regulations to be able to use the name. It's possible that Shell owns the land and the building and the "owner" of the place is paying them rent on it, and doing repair work there. Shell would know who the owner is, and would be very interested to know about this situation.
2. Call the station again, tell them to give you the owner's name/phone number, and let them know that this is the last chance they have to do so properly, but don't bother threatening them. Just let them know that they won't have another shot, and if they don't come through then get ahold of your state's attorney general's office and talk to them. These guys are blatently lying to you, they know who pays them, they just don't care. They had an obvious safety hazard there, and they ruined your jacket, and now they're simply avoiding dealing with it. The AG can help with this if they aren't willing to own up.
3. If all else fails, contact a local lawyer, many will listen to you for free and determine if it's worth them helping you. If it is, they can deal with the station for replacement of your jacket as well as their own fees. I stress that this is a LAST option only, you got pictures of the hose which is good, and I'd recommend getting pictures of the jacket and/or a dry-cleaners estimate on it, or at least something from them saying it's un-cleanable. That way even if this takes a month or two to clear up, you have evidence down the line. Get a picture of the pump covered up as well, and keep track of how long it took them to do that and all of your communications with the station.