1) I would think the FAQ question about why a loan to purchase a lot with a dwelling to knock down and build a dwelling for sale has a corollary that if the dwelling wasn't there, then the loan could be excluded, so I like to think this falls under the exclusion. Purchasing the land is part of the construction process as it were.
2/3) I've never run into this personally. Generally, a spec home loan is just that and not other stuff wrapped into it. That would be tricky to navigate. I think your #3 gets to what the intent of the reg is, but it's not really what the words say, so I'm not sure what the CFPB would say.
4) Corporations are people too.