We've had goats that would give a gallon or more a day and we usually fed them the same mixed hay as the horses. As much as they'll eat unless they're getting too fat.
We do mix alfalfa pellets to the goats feed when they were milked twice a day. Then the goat can be eating the whole time you're milking, but not get too much grain.
They also go out on pasture some, but if you have funny tasting weeds once you're drinking the milk you'll notice it tastes weird lol.
I would also make sure they have free choice salt and goat minerals.
As far as the uneven udder, as you know, that comes from the kid only drinking off of one side. That very well can give a goat mastitis and the previous owners should have been milking it twice a day on both sides all along to prevent that and keep the udder even. A well bred dairy goat produces much too much milk for one baby anyway and even if the baby is drinking evenly it likely will not drink enough. In a best case scenerio it will cut down the doe's future milk production, but it can cause other problems as well.
Along with the signs of mastitis that have already been mentioned you will also want to make sure one side of the udder is not hotter than the other as this can also be an indication.
We leave our goats collars on. They are either the plastic link or dog collars and we've never had a problem that way.
Goats usually don't need dewormed as often as horses. It depends on a lot of factors though, including your area so you're going to have to do more research on yours. Generally you have to toss the milk for a while after deworming. We give some of it to the cats. Depending on the dewormer you may be able to use the milk for the foal though.
Be wary, some worms that have little affect on other animals can kill a goat in a short time. Know what you have in your area. Some really need to be prevented rather than taken care of later. Read a lot on this subject.
I love how shiny and healthy your new goats look :)
I would be asking their previous owners lots of questions...
Goats are not my thing, ours belong to my mother. I just do the dirty work like giving shots, trimming hooves, and helping with any medical issues they might have (which is rare). I am no expert, but have a LOT of hands on experience with some pretty nice sannans. They are stubborn creatures by nature but just like anything else, with good training and proper care they come around :)
I wish you the best of luck with yours and I hope you love them!