Personally, I am using Fluval shrimp stratum mixed with Laterite (there is also regular gravel underneath that, too. I know, way too much substrate...). I just didn't feel like taking out the Laterite. It works fine and I haven't had any problems with their barbels at all, at least, none that I ever noticed. I have 9 cories and have had some so long that they died of old age, so, I would say that it is safe. It is about 18 bucks on Amazon for 4.4 pounds, or 8.8 pounds for $21. It is a dark brown color. Not as dark as the BDBS, but, I do think it is close enough that you would be happy with it.
I have no personal experience with them growing back, but, according to these threads, they do, just not to the size they were before injured (a couple people mentioned this), but, as I haven't owned one with injured barbels, I can't comment on whether that is true or not.
Here's some other links talking about this, too.
Corydoras With No Barbels - PlanetCatfish.com
According to all these threads, they will! I guess that is good news for you. 1 person said that it took over 6 months for them to grow back, so, I guess just be patient. Another comment says that Cory's do use them to hunt for food, so, just watch the one without barbels and make sure that it is eating enough. You should keep an eye on him daily. I do agree with that, it may have a little trouble finding food, but, as food is given to him daily (or whatever your schedule is) it shouldn't be too big of a problem, imo. Like I just said, just make sure it is getting enough food and keep an eye on him. He should be fine, though. I would (personally) get some of Kordon's Fish Protector and add it every day or two for a little bit, or maybe Melafix. Something like that. I have one that has long fins and his fins got injured. His fins started to rot away and the Fish Protector has made a significant difference. Stopped the rot dead in it's tracks.
As far as the stratum goes, it seems like it is perfect for plants. It has a lot of nutrients in it and it has the consistency of dirt or clay. It is little pebbles and it will compact over time, but, not so much that the plants get their roots through it. I used to use just plain laterite on top and never had any problems, as far as the cory's were concerned. I hope this doesn't come off as conceited, but, I have used a lot of different types of substrate and never had a problem with this, but, I always kept it in the back of my mind when looking for a substrate, meaning, I made sure that it wasn't sharp because I knew that I would have a cory or two in there. Again, I don't want that to come off as being cocky, mean or anything like that.
I would like to ask you this: what kind of plants are you growing in your tank? The stratum is good (imo) for stuff like Crypts and other plants that feed through their roots. I have 2 Crypt Wendtii's (green and red) a few Parva's and others that root feed and they all do great with this. I just have an inch or two on top of waaaayyyyy too much substrate, so, depending on how much substrate you have already, you could just put a small layer of this stratum on top of what is already there, kind of like I did.
I have also used regular rounded aquarium gravel in the past and haven't had any issues. I have used Laterite and no issues with the cory's either. I hope this helps you in some way. Good luck with your tank, I hope it does well!
Edit-I always keep Cory's, I just love them! I have kept them my whole life in every last aquarium I have had, that is about 30 years! I just love them, they look like an old man with a beard, I just love those guys!
Also, the common answer to this will probably be just sand (you can always add some Flourish tabs to it if you want to), I think, but, what I have said above is just my experience with Corydoras. Good luck!
Edit 2: Since this is a thread about cory's and there is the problem of him eating enough, I wanted to add this. I recently got this off of Amazon https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
They are tubifex worms and are shaped into a cube. They are on sale for $7 and usually sell for $8.50. I have been taking a cube with those long, aquascaping tweezers and holding at the bottom so that the cory's can come and eat it. They absolutely LOVE them!!! The other fish get a treat as well, because the cory's knock off a bunch of worms while they themselves are trying to eat them. It is SO much fun! I thought maybe you could do this with the one that lost his barbels? It would be a great source of protein for him to heal with and it is just a whole ton of fun to do! I tap the tweezers against the glass and they learn after doing this once or twice that it is feeding time and come running. Once they are done eating, all mine sit in a row on the bottom. Just a thought, this way you can be certain that he is getting food. I really hope he makes it and doesn't die on you. I would appreciate it if you let us know how he does. Good luck!