I'll try and answer as far as I can
Whilst I'm sure the cast will resist wear it must inevitably depend on the types of surface and conditions. There is a leaflet on the same site as the video which makes this point re barefoot. I presume this is why the "plastic shoe" made from polyurethane cement was developed. It acts as a sacrificial wear plate, much as a metal shoe, but without the nails, and protects the cast from premature wear as well as providing grip. Its also very easy to add a further layer of "cement" if it does wear too much.
I can't imagine the casts can be reused. Those I have seen removed are just "peeled off" by the farrier using a pair of 14" nips. My impression is that after 6 weeks or so the growth of the foot and natural losses from the surface of the horn means it comes off with a bbit of leverage. In the first couple of weeks after application it is very hard to get off- as the farrier in the video says "you will need a pneumatic drill". I don't know if you have ever got a really good glue on your skin, at first its very difficult to get off but natural growth and "shedding" processes means that a few days later it peels off easily. I guess the same with hoof horn, the growth and "shedding" is just much slower than with human skin.
As for screwing studs into the cast, I don't know but I suspect its too thin by itself but a 5mm layer of the "plastic cement" on the bearing surface may make this realistic , but I really don't know, I've not seen it done. Being a boffin I prefer experimental data to unsupported hypothesis. I can't imagine that it is too difficult for you to try and let everyone know how you get on.
If I may a few futher points about formaldehyde. I should make it clear that formaldehyde has its place. It's a very good disinfectant -still used for this for foot rot on cattle and sheep- and some hardness is not a bad thing. Howvever it should be used in combination with other things , such as are used for human nail hardeners. The chemistry is essentially identical but the reagents used on humans build in toughness and resilience not just hardness. They are though much more expensive. Mind you at £25 a bottle it must be possible!
I believe this may be what is behind the product ex Endurance UK Barefoot Champion Les Spark has on his website. Take a look, its an interesting site anyway and Les is very friendly, just email him and ask him what he thinks.
http://www.fnesaddles.com/Hooves-Barefoot.shtml.
As for breeding in better hooves, well, a good idea in principle but it will take at least 50 years and until then we will have to deal with the animal in front of us today. Unfortunately I just don't think it likely that breeding programs for racehorses are going to put hooves high up the selection criteria for traits to be selected for in choosing parents. I don't think it is totally ignored but other things are seen as more important. The rather famous stallion Mtoto had a good racing career and has sired quite a few high class winners. His feet were awful and so are many of his progenies eg Alfresco. But they keep winning which is what the breeders and owners focus on.
What we often forget is that millions of years of evolution went into the horse, largely suiting it for arid regions not the wet western continental climate we insist our horses live in. I think that excessive moisture and numerous wet-dry cycles are responsible for many of the foot issues we see in our horses that are rare where the climate is basically very dry. It doesn't matter if its hot or cold so long as its dry. Try taking a horse or a donkey to the tropics, their feet fall off in months. The warmth and moisture soften the hooves and encourage bacteria and the feet soon rot. Its not quite so bad in the UK as its often cold and not quite so wet so we get away with it most of the time, but it can be marginal. However if we get a warm wet spring next year after all the moisture this year, look out !
