Well my first question would be is the deposit refundable? If not you might not want to waste the money and just stick it out, there are some red flags but nothing completely terrible. Tf they will issue a refund though you might want to take it and look elsewhere. There was some other breeders mentioned on another one of your threads, you might want to check them out.
The thing with pet store chins is they do technically come from breeders, at least ones you get from big box stores like petco and petsmart. The stores put in an order and local breeders and ranchers sell off some of their chins. But most places don't know or wont say where the chins came from, so they could have come from a good local breeder that is just selling off "pet quality" but otherwise perfectly healthy kits from their show breeding lines, or could be a large scale pelt farm that doesn't care about long term health or lifespan selling off excess kits, or anything in between. So it's not so much they aren't healthy it's that you have no idea of the health, and no way of knowing genetic health. Also most pet store don't properly care for the chins they get in, so they are more likely to have issues like ringworm (from other animals and living in poorly ventilated glass tanks), giardia (from being given tap water if it's contaminated), as well as digestive issues from improper diet (fruits and veggies are commonly given) and also can possibly have a gut blockage from plastic, paper bedding, and/or cardboard that the store put in with them. The improper care can be navigated around somewhat by specifically ordering a chinchilla from the pet store or having them give you a call when then get chins in, so the chin is in the store for as short of a period as possible. That being said though, there are plenty of people that have gotten chins from pet stores and they lived perfectly fine and long lives into their teens.
With a breeder they should be able to give you the genetic history of the chins they breed, so you know if issues like malo run in the lines or not. Most breeders also try to be better about keeping on top of issue like ringworm or giardia, but they do happen, they also tend to be a lot more strict on what goes in the cage then even pet owners are, so much less likely to have been given unsafe items to chew on.
Getting a kit just increases the chance that they haven't been mistreated, it doesn't really increase the strength of the bond. Bonding with a chin can still take time and patience, it's something that is built over years. How social and friendly they are all comes down to personality and how they are treated. The chin I had the closest bond with I got as a rescued adult. Although a kit is a bit more sensitive to heat then an adult (like a human baby is more sensitive to heat then a few year old child) the temp should always be kept below the max temp (below about 75F with low humidity), so it shouldn't really be any more of an issue then if you had an adult chin. I like to keep the room at or below 68F so that if the power go out or the AC dies or something I have some wiggle room on the temp to give me time to figure something out before it gets dangerous for them. Since you are worried about a young kit you can look around and see if any breeders maybe have a kit closer to 4-6 months old that maybe didn't sell or they wanted to hold back to see how they grow as a show prospect, but have decided to sell them. Still young enough to hopefully only have known a good life but old enough to be a bit more temp tolerant.