They're called hold-open washers.
It won't be easy to assume based on your description. Perhaps post a photo of where the washer normally meets the metal?
It sounds like the washer is probably just bent. Maybe you can take it off and straighten it in a vice and try it again. If it comes down to it, and you want to save some money.. you can back the set screw out of a drill stop and put a thumb screw in, grind the lugs off the shaft and slide it on!
If the door panel, the moving part, is not clad (covered with metal) on the outside, the easiest way to remedy the problem is to plane about an 1/8" off the door itself. The weather-stripping is part of the jamb so it will not be affected. The interior side of the track will have a few screws holding it place. I see one screw hole in the picture, looks like it is missing the screw. Remove the rest, that piece should come out, and the door panel with it. If there is a place in the jamb where the door is loose compared to the other places, move the door to there to get the top to tip out, it will be heavy...
As a note I would draw some concern why the head is dropping, unless the bottom sill that the door rides on is rising. Either will cause the same problem. Swelling wood from leaks in the siding or flashing or other things that happen over time.
Although this will not address the potential problem, that is, why the head has dropped, if that is why the door head drags, you may be able to run a few 3" screws into the track at the top and draw it up a little, that way if there is any room for it to go up, that will make that happen. Do not put the screws in the middle of the jamb, do put them in the middle of the operable track that the sliding door panel rides in. Headers are usually made with 2 pieces, with a 1/2" space in the middle. That's why no screws in the middle.
If the sill is raised up, check to confirm with a real true, stable, straight edge. If it is riding up in the middle, that is bad, usually there are no ways to send a sill down, usually they are set in sealant, and gravity does the rest. Very few have screws set to them, it is a leak potential.
Best Answer
The flash point of a material is the temperature above which it will give off vapors that can ignite. It's NOT the temperature at which the fumes or the material will self-ignite. As a point of reference, you likely handle gasoline regularly and its flash point is -45F!
Just ensure that there are no ignition sources while you are using the product and have plenty of ventilation (should not be an issue at an outside door) while using it to prevent fumes from building up.
Answers to your questions:
The can should have storage information but I suspect it says "cool dry place".
Again the container should have disposal information but you may want to handle it as you would paint or a similar substance and dispose of it at a hazardous household waste disposal site in your community.
It's NEVER a good idea to wash solvents into your sink. Capture solvents you wash things with and dispose of at a suitable waste disposal site.
Yes, that would be reasonable.