I'm so glad to hear your pet is healthy. I was also very concerned that something may have been lodged in its throat.
UV light is an interesting idea. In fact our vet (at the time) recommended one for our African Grey parrot and sold us one (and not at a good price). It actually caused artificial sunburn on our bird's face, which, on a Grey, is not covered by feathers. At first we thought it was a reaction to a probiotic they put him on at the time, but it happened several times afterwards and it was very funny looking.
We later looked it up and discovered that as long as his diet was good he didn't need it, and that the artificial light could actually be harmful because the UV emission can be way too high depending on the bulb's construction and cause skin damage and cataracts. And, because there are no regulations, there is no way to know how much light was output so we stopped using it.
As far as chinchillas go there is only one exposed area on them, their eyes, that sunlight can reach, and they are animals that in nature hide under rocks during the day and sleep and come out only when it is dark to avoid predators. I am not saying what you should or should not do but I hope you find this information useful.
As far as hay goes if it looks green and smells fresh you are good to go. Hay that has been sitting on the shelf too long will not be green. Hay that smells damp, or even the slightest bit off, should be replaced immediately and without question. I learned that the hard way this year. I always open the bag at the store and smell it before I buy it. If it is off I take it to the counter and point it out. Around here moisture is a problem no matter what store you get it from.
Wire ramps or wire shelves in the cage are bad news no matter what. Chinchillas get tangled up in these and break their legs and feet. I see reports of this regularly on these boards. Use solid white pine boards cut to size and mounted to minimize gaps. Chinchillas don't need ramps since they can jump straight up and prefer that. They can be tilted downward so the mess falls towards the inside of the cage. Once you install a couple of shelves you should see improvement on the foot pads in a two or three weeks. I had a chinchilla that rested on wire shelves before I bought him. It took about two months before I noticed improvement but he also had a habit of sleeping on the wire floor. That changed once I removed the wooden hut he liked to sleep under and then he preferred the shelves.
It actually is ideal to vary hay grasses, although, for other things, it is best to not vary your pet's diet. When you switch pellets try to switch gradually over two weeks if you can.
You can Heimlich a chinchilla like you can a rabbit. I'll leave it up to you to search on that one because it's a precarious maneuver that is difficult to do safely.
